serial: of_serial: Handle auto-flow-control property

- no-loopback-test: set to indicate that the port does not implements loopback

  test mode

- fifo-size: the fifo size of the UART.

- auto-flow-control: one way to enable automatic flow control support. The

  driver is allowed to detect support for the capability even without this

  property.

Example:

#include <linux/slab.h>

#include <linux/delay.h>

#include <linux/serial_core.h>

#include <linux/serial_8250.h>

#include <linux/serial_reg.h>

#include <linux/of_address.h>

#include <linux/of_irq.h>

#include <linux/nwpserial.h>

#include <linux/clk.h>

#include "8250/8250.h"

struct of_serial_info {

	struct clk *clk;

	int type;

#ifdef CONFIG_SERIAL_8250

	case PORT_8250 ... PORT_MAX_8250:

	{

		/* For now the of bindings don't support the extra

		   8250 specific bits */

		struct uart_8250_port port8250;

		memset(&port8250, 0, sizeof(port8250));

		port8250.port = port;

		if (port.fifosize)

			port8250.capabilities = UART_CAP_FIFO;

		if (of_property_read_bool(ofdev->dev.of_node,

					  "auto-flow-control"))

			port8250.capabilities |= UART_CAP_AFE;

		ret = serial8250_register_8250_port(&port8250);

		break;

	}