ext4: fix mount option parsing

The "resize" option won't be noticed as it comes after the NULL option,
so if you try to mount (or in this case remount) with that option it
won't be recognized.

Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Josef Bacik <jbacik@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>