[media] vb2: fix PREPARE_BUF regression

Fix an incorrect test in vb2_internal_qbuf() where only DEQUEUED buffers
are allowed. But PREPARED buffers are also OK.

Introduced by commit 4138111
("vb2: simplify qbuf/prepare_buf by removing callback").

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/v4l2-core/videobuf2-core.c

@@ -1459,11 +1459,6 @@ static int vb2_internal_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
 		return ret;
 
 	vb = q->bufs[b->index];
-	if (vb->state != VB2_BUF_STATE_DEQUEUED) {
-		dprintk(1, "%s(): invalid buffer state %d\n", __func__,
-			vb->state);
-		return -EINVAL;
-	}
 
 	switch (vb->state) {
 	case VB2_BUF_STATE_DEQUEUED:
@@ -1477,7 +1472,8 @@ static int vb2_internal_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
 		dprintk(1, "qbuf: buffer still being prepared\n");
 		return -EINVAL;
 	default:
-		dprintk(1, "qbuf: buffer already in use\n");
+		dprintk(1, "%s(): invalid buffer state %d\n", __func__,
+			vb->state);
 		return -EINVAL;
 	}