V4L/DVB (5983): Arv.c: fix memset in ioctl

Looks like memset() is zeroing wrong nr of bytes.
Signed-off-by: Mariusz Kozlowski <m.kozlowski@tuxland.pl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/video/arv.c

@@ -441,7 +441,7 @@ static int ar_do_ioctl(struct inode *inode, struct file *file,
 	{
 		struct video_window *w = arg;
 		DEBUG(1, "VIDIOCGWIN:\n");
-		memset(w, 0, sizeof(w));
+		memset(w, 0, sizeof(*w));
 		w->width = ar->width;
 		w->height = ar->height;
 		return 0;