drm/cma-helper: Export dedicated wrappers for GEM object functions

Wrap GEM CMA functions for struct drm_gem_object_funcs and update
all callers. This will allow for an update of the public interfaces
of the GEM CMA helper library.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20211115120148.21766-3-tzimmermann@suse.de