This patch unifies the naming of DRM functions for reference counting
of struct drm_gem_object. The resulting code is more aligned with the
rest of the Linux kernel interfaces.

v2:
	* rebase onto fbdev rework
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: http://patchwork.freedesktop.org/patch/msgid/20180926113623.22679-1-tzimmermann@suse.deSigned-off-by: Gerd Hoffmann <kraxel@redhat.com>