[media] em28xx: Don't initialize a var if won't be using it

Fixes most cases of initializing a var but not using it.

There are still 3 cases at em28xx-alsa, were those vars should
probably be used.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/video/em28xx/em28xx-cards.c b/drivers/media/video/em28xx/em28xx-cards.c
index 7635a45..bbd67d7 100644
--- a/drivers/media/video/em28xx/em28xx-cards.c
+++ b/drivers/media/video/em28xx/em28xx-cards.c
@@ -2660,10 +2660,9 @@
 			.addr = 0xba >> 1,
 			.platform_data = &pdata,
 		};
-		struct v4l2_subdev *sd;
 
 		pdata.xtal = dev->sensor_xtal;
-		sd = v4l2_i2c_new_subdev_board(&dev->v4l2_dev, &dev->i2c_adap,
+		v4l2_i2c_new_subdev_board(&dev->v4l2_dev, &dev->i2c_adap,
 				&mt9v011_info, NULL);
 	}