drivers: iio: dac: Fix sparse warning

Fixing below warnings:

drivers/iio/dac/ad5592r.c:58:41: warning: incorrect type in argument 2 (different base types)
drivers/iio/dac/ad5592r.c:58:41:    expected unsigned short [usertype] *buf
drivers/iio/dac/ad5592r.c:58:41:    got restricted __be16 *<noident>
drivers/iio/dac/ad5592r.c:62:41: warning: incorrect type in argument 2 (different base types)
drivers/iio/dac/ad5592r.c:62:41:    expected unsigned short [usertype] *buf
drivers/iio/dac/ad5592r.c:62:41:    got restricted __be16 *<noident>
drivers/iio/dac/ad5592r.c:92:41: warning: incorrect type in argument 2 (different base types)
drivers/iio/dac/ad5592r.c:92:41:    expected unsigned short [usertype] *buf
drivers/iio/dac/ad5592r.c:92:41:    got restricted __be16 *<noident>
drivers/iio/dac/ad5592r.c:110:41: warning: incorrect type in argument 2 (different base types)
drivers/iio/dac/ad5592r.c:110:41:    expected unsigned short [usertype] *buf
drivers/iio/dac/ad5592r.c:110:41:    got restricted __be16 *<noident>

Signed-off-by: Sandhya Bankar <bankarsandhya512@gmail.com>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/dac/ad5592r.c

@@ -17,7 +17,7 @@
 #define AD5592R_GPIO_READBACK_EN	BIT(10)
 #define AD5592R_LDAC_READBACK_EN	BIT(6)
 
-static int ad5592r_spi_wnop_r16(struct ad5592r_state *st, u16 *buf)
+static int ad5592r_spi_wnop_r16(struct ad5592r_state *st, __be16 *buf)
 {
 	struct spi_device *spi = container_of(st->dev, struct spi_device, dev);
 	struct spi_transfer t = {