video/aty/atyfb_base.c: free when fb can't be registered

Free buffer when the framebuffer can't be registered

Signed-off-by: Roel Kluin <12o3l@tiscali.nl>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>