kmsro: Move DRM entrypoints to shared block

kmsro: Move DRM entrypoints to shared block

As kmsro allows an essentially mix-and-match hodgepodge of display
drivers and renderonly GPUs, it doesn't make sense to couple the display
driver entrypoint definition with the driver. Instead, we move *all*
kmsro entrypoints to a shared kmsro block at the end (avoiding clutter
and distraction since this list may snowball in the future).

v2: Alphabetize driver list.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Eric Anholt <eric@anholt.net>