iio: ad5504: Remove redundant variable

By re-arranging the code, 'ret' can be removed from this
function.

Signed-off-by: Sachin Kamat <[e-mail]>
Acked-by: Lars-Peter Clausen <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/dac/ad5504.c

···
 			       long mask)
 {
 	struct ad5504_state *st = iio_priv(indio_dev);
-	int ret;
 
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
···
 
 		return ad5504_spi_write(st, chan->address, val);
 	default:
-		ret = -EINVAL;
+		return -EINVAL;
 	}
-
-	return -EINVAL;
 }
 
 static const char * const ad5504_powerdown_modes[] = {