iio: mma8452: Add access to registers via DebugFS

#define MMA8452_CTRL_REG2 0x2b

#define MMA8452_CTRL_REG2_RST		BIT(6)

#define MMA8452_MAX_REG 0x31

#define MMA8452_STATUS_DRDY (BIT(2) | BIT(1) | BIT(0))

#define MMA8452_CTRL_DR_MASK (BIT(5) | BIT(4) | BIT(3))

	return IRQ_HANDLED;

}

static int mma8452_reg_access_dbg(struct iio_dev *indio_dev,

				  unsigned reg, unsigned writeval,

				  unsigned *readval)

{

	int ret;

	struct mma8452_data *data = iio_priv(indio_dev);

	if (reg > MMA8452_MAX_REG)

		return -EINVAL;

	if (!readval)

		return mma8452_change_config(data, reg, writeval);

	ret = i2c_smbus_read_byte_data(data->client, reg);

	if (ret < 0)

		return ret;

	*readval = ret;

	return 0;

}

#define MMA8452_CHANNEL(axis, idx) { \

	.type = IIO_ACCEL, \

	.modified = 1, \

	.attrs = &mma8452_group,

	.read_raw = &mma8452_read_raw,

	.write_raw = &mma8452_write_raw,

	.debugfs_reg_access = &mma8452_reg_access_dbg,

	.driver_module = THIS_MODULE,

};