fbmem: Check failure of FBIOPUTCMAP ioctl

On FBIOPUTCMAP ioctl failure deallocate
fb cmap. Put null check for cmap red, green,
blue component.

Change-Id: I10468ee30d0e76c256cf3d7a6ffe14db7fd4511b
Signed-off-by: Pawan Kumar <pavaku@codeaurora.org>