[media] v4l: drop v4l2_buffer.input and V4L2_BUF_FLAG_INPUT

Remove input field in struct v4l2_buffer and flag V4L2_BUF_FLAG_INPUT which
tells the former is valid. The flag is used by no driver currently.

Also change the documentation accordingly.

Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
index f79d0cc..a61edb3 100644
--- a/include/linux/videodev2.h
+++ b/include/linux/videodev2.h
@@ -657,7 +657,7 @@
 		struct v4l2_plane *planes;
 	} m;
 	__u32			length;
-	__u32			input;
+	__u32			reserved2;
 	__u32			reserved;
 };
 
@@ -671,7 +671,6 @@
 /* Buffer is ready, but the data contained within is corrupted. */
 #define V4L2_BUF_FLAG_ERROR	0x0040
 #define V4L2_BUF_FLAG_TIMECODE	0x0100	/* timecode field is valid */
-#define V4L2_BUF_FLAG_INPUT     0x0200  /* input field is valid */
 #define V4L2_BUF_FLAG_PREPARED	0x0400	/* Buffer is prepared for queuing */
 /* Cache handling flags */
 #define V4L2_BUF_FLAG_NO_CACHE_INVALIDATE	0x0800