drm/nouveau-misc: display patches.

These are just some precursor and cleanup display patches from Ben,
tested by Lyude.
Signed-off-by: Dave Airlie <airlied@redhat.com>

From: Dave Airlie <airlied@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/CAPM=9ty0R37q0mohBr_CegpYLXK2=fAH54QfAsMhHfPygTsdQA@mail.gmail.com