staging: iio: ad9832: Remove redundant check

'val' is unsigned and cannot be negative.
Signed-off-by: Sachin Kamat <sachin.kamat@samsung.com>
Cc: Michael Hennerich <hennerich@blackfin.uclinux.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/frequency/ad9832.c

@@ -120,7 +120,7 @@ static ssize_t ad9832_write(struct device *dev, struct device_attribute *attr,
 		ret = spi_sync(st->spi, &st->msg);
 		break;
 	case AD9832_PHASE_SYM:
-		if (val < 0 || val > 3) {
+		if (val > 3) {
 			ret = -EINVAL;
 			break;
 		}