drm: Ignore drm_gem_vram_mm_funcs in generated documentation

The documentation tools interpret drm_gem_vram_mm_funcs as function and
there appears to be no way of inline-documenting constants. This results
in a warning by 'make htmldocs'. For now, removing drm_gem_vram_mm_funcs
from generated documentation works around the issue.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: http://patchwork.freedesktop.org/patch/msgid/20190604111330.25324-1-tzimmermann@suse.de


Fixes: 5c9dcacf ("drm: Add default instance for VRAM MM callback functions")
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>