Staging: iio: adc: fix indent on break statement

Fix indent warning when building with gcc 6:
drivers/staging/iio/adc/ad7192.c:239:4: warning: statement is indented
  as if it were guarded by... [-Wmisleading-indentation]
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/adc/ad7192.c

@@ -236,7 +236,7 @@ static int ad7192_setup(struct ad7192_state *st,
 			st->mclk = pdata->ext_clk_hz;
 		else
 			st->mclk = AD7192_INT_FREQ_MHZ;
-			break;
+		break;
 	default:
 		ret = -EINVAL;
 		goto out;