sunxvr500: fix cmap memory leaks

- fix cmap leak in removal path
 - fix cmap leak when register_framebuffer fails

Signed-off-by: Andres Salomon <dilinger@debian.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>