iio: dac: ad5360: use int type to store negative error codes

Change the 'ret' variable in ad5360_update_ctrl() from unsigned int to
int, as it needs to store either negative error codes or zero returned
by ad5360_write_unlocked().

Fixes: a3e2940c24d3 ("staging:iio:dac: Add AD5360 driver")
Signed-off-by: Qianfeng Rong <[e-mail]>
Reviewed-by: Andy Shevchenko <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Cc: <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/dac/ad5360.c

···
 	unsigned int clr)
 {
 	struct ad5360_state *st = iio_priv(indio_dev);
-	unsigned int ret;
+	int ret;
 
 	mutex_lock(&st->lock);