of_spi: add generic binding support to specify cs gpio

- #size-cells     - should be zero.

- compatible      - name of SPI bus controller following generic names

    		recommended practice.

- cs-gpios	  - (optional) gpios chip select.

No other properties are required in the SPI bus node.  It is assumed

that a driver for an SPI bus device will understand that it is an SPI bus.

However, the binding does not attempt to define the specific method for

Optional property:

- num-cs : total number of chipselects

If cs-gpios is used the number of chip select will automatically increased

with max(cs-gpios > hw cs)

So if for example the controller has 2 CS lines, and the cs-gpios

property looks like this:

cs-gpios = <&gpio1 0 0> <0> <&gpio1 1 0> <&gpio1 2 0>;

Then it should be configured so that num_chipselect = 4 with the

following mapping:

cs0 : &gpio1 0 0

cs1 : native

cs2 : &gpio1 1 0

cs3 : &gpio1 2 0

SPI slave nodes must be children of the SPI master node and can

contain the following properties.

- reg             - (required) chip select address of device.

- spi-cs-high     - (optional) Empty property indicating device requires

    		chip select active high

If a gpio chipselect is used for the SPI slave the gpio number will be passed

via the cs_gpio

SPI example for an MPC5200 SPI bus:

	spi@f00 {

		#address-cells = <1>;

#include <linux/slab.h>

#include <linux/mod_devicetable.h>

#include <linux/spi/spi.h>

#include <linux/of_gpio.h>

#include <linux/pm_runtime.h>

#include <linux/export.h>

#include <linux/sched.h>

	spi->dev.parent = &master->dev;

	spi->dev.bus = &spi_bus_type;

	spi->dev.release = spidev_release;

	spi->cs_gpio = -EINVAL;

	device_initialize(&spi->dev);

	return spi;

}

int spi_add_device(struct spi_device *spi)

{

	static DEFINE_MUTEX(spi_add_lock);

	struct device *dev = spi->master->dev.parent;

	struct spi_master *master = spi->master;

	struct device *dev = master->dev.parent;

	struct device *d;

	int status;

	/* Chipselects are numbered 0..max; validate. */

	if (spi->chip_select >= spi->master->num_chipselect) {

	if (spi->chip_select >= master->num_chipselect) {

		dev_err(dev, "cs%d >= max %d\n",

			spi->chip_select,

			spi->master->num_chipselect);

			master->num_chipselect);

		return -EINVAL;

	}

		goto done;

	}

	if (master->cs_gpios)

		spi->cs_gpio = master->cs_gpios[spi->chip_select];

	/* Drivers may modify this initial i/o setup, but will

	 * normally rely on the device being setup.  Devices

	 * using SPI_CS_HIGH can't coexist well otherwise...

}

EXPORT_SYMBOL_GPL(spi_alloc_master);

#ifdef CONFIG_OF

static int of_spi_register_master(struct spi_master *master)

{

	u16 nb;

	int i, *cs;

	struct device_node *np = master->dev.of_node;

	if (!np)

		return 0;

	nb = of_gpio_named_count(np, "cs-gpios");

	master->num_chipselect = max(nb, master->num_chipselect);

	if (nb < 1)

		return 0;

	cs = devm_kzalloc(&master->dev,

			  sizeof(int) * master->num_chipselect,

			  GFP_KERNEL);

	master->cs_gpios = cs;

	if (!master->cs_gpios)

		return -ENOMEM;

	memset(cs, -EINVAL, master->num_chipselect);

	for (i = 0; i < nb; i++)

		cs[i] = of_get_named_gpio(np, "cs-gpios", i);

	return 0;

}

#else

static int of_spi_register_master(struct spi_master *master)

{

	return 0;

}

#endif

/**

 * spi_register_master - register SPI master controller

 * @master: initialized master, originally from spi_alloc_master()

	if (!dev)

		return -ENODEV;

	status = of_spi_register_master(master);

	if (status)

		return status;

	/* even if it's just one always-selected device, there must

	 * be at least one chipselect

	 */

	void			*controller_state;

	void			*controller_data;

	char			modalias[SPI_NAME_SIZE];

	int			cs_gpio;	/* chip select gpio */

	/*

	 * likely need more hooks for more protocol options affecting how

	int (*transfer_one_message)(struct spi_master *master,

				    struct spi_message *mesg);

	int (*unprepare_transfer_hardware)(struct spi_master *master);

	/* gpio chip select */

	int			*cs_gpios;

};

static inline void *spi_master_get_devdata(struct spi_master *master)