drm/compat: more dummy implementations

drm_noop really doesn't do much, and who cares about the permission checks.
So let's delete some code.

Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210222100608.400730-1-daniel.vetter@ffwll.ch