V4L/DVB (4510): Fix signedness error in drivers/media/video/vivi.c

when checking the -Wextra signedness warnings issued by gcc 4.1
I came across this one:
drivers/media/video/vivi.c:1001: warning: comparison of unsigned expression < 0 is always false
Since videobuf_reqbufs() returns negative values on errors the current
code does no real error checking since gcc removes the comparison.
This patch fixes this issue by making ret a normal, signed integer.
Signed-off-by: Eric Sesterhenn <snakebyte@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/video/vivi.c

@@ -992,7 +992,8 @@ static int vidiocgmbuf (struct file *file, void *priv, struct video_mbuf *mbuf)
 	struct vivi_fh  *fh=priv;
 	struct videobuf_queue *q=&fh->vb_vidq;
 	struct v4l2_requestbuffers req;
-	unsigned int i, ret;
+	unsigned int i;
+	int ret;
 
 	req.type   = q->type;
 	req.count  = 8;