[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/drivers/media/video/videobuf2-core.c b/drivers/media/video/videobuf2-core.c
index 9d4e9ed..ec24718 100644
--- a/drivers/media/video/videobuf2-core.c
+++ b/drivers/media/video/videobuf2-core.c
@@ -336,9 +336,9 @@
 	struct vb2_queue *q = vb->vb2_queue;
 	int ret;
 
-	/* Copy back data such as timestamp, flags, input, etc. */
+	/* Copy back data such as timestamp, flags, etc. */
 	memcpy(b, &vb->v4l2_buf, offsetof(struct v4l2_buffer, m));
-	b->input = vb->v4l2_buf.input;
+	b->reserved2 = vb->v4l2_buf.reserved2;
 	b->reserved = vb->v4l2_buf.reserved;
 
 	if (V4L2_TYPE_IS_MULTIPLANAR(q->type)) {
@@ -860,7 +860,6 @@
 
 	vb->v4l2_buf.field = b->field;
 	vb->v4l2_buf.timestamp = b->timestamp;
-	vb->v4l2_buf.input = b->input;
 	vb->v4l2_buf.flags = b->flags & ~V4L2_BUFFER_STATE_FLAGS;
 
 	return 0;