drm/cirrus: kick out conflicting framebuffers earlier

It appears that grub2 will pass framebuffer info via EFI,
this causes the vram reserve to fail, so kick out efifb
earlier before cirrus loads.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=826983


Signed-off-by: Dave Airlie <airlied@redhat.com>