V4L/DVB (7732): vivi: fix a warning

some gcc versions complain that fh is used without being defined.

The error report is bogus. However, fixing it is trivial. Better to make
gcc happy.
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/video/vivi.c

@@ -888,7 +888,7 @@ static int vivi_open(struct inode *inode, struct file *file)
 {
 	int minor = iminor(inode);
 	struct vivi_dev *dev;
-	struct vivi_fh *fh;
+	struct vivi_fh *fh = NULL;
 	int i;
 	int retval = 0;