drm: fb: cma: fix memory leak

We may have a situation that the memory allocation for fbdefio fails
and then the allocation for fbops may succeed as some memory has been
freed somewhere. Lets free fbops also to face these rare situtation.
Since kfree can handle arguments as NULL, there should not be any
problem in calling both the kfree().

Signed-off-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Fixes: 199c7717 ("drm/fb-cma-helper: Add fb_deferred_io support")
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1465743836-6228-1-git-send-email-sudipm.mukherjee@gmail.com