video: Fix use-after-free by vga16fb on rmmod

video: Fix use-after-free by vga16fb on rmmod

commit a50d28de8d5085e0f34f96088a45cc156d022021 upstream.

Since fb_info is now refcounted and thus may get freed at any time it
gets unregistered module unloading will try to unregister framebuffer
as stored in platform data on probe though this pointer may
be stale.

Cleanup platform data on framebuffer release.

Signed-off-by: Bruno Prémont <bonbons@linux-vserver.org>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>