drm: Merge branch 'drm-cleanups-jbarnes' into drm-core-next

drm: Merge branch 'drm-cleanups-jbarnes' into drm-core-next

Merge topic branch with some of Jesse's cleanups, the save/restore hooks
were being used by GMA500 so we can't just drop them.

* drm-cleanups-jbarnes:
  drm: remove some potentially dangerous DRM_ERRORs
  drm: document the drm_mode_config structure
  drm: document the drm_mode_group structure
  drm: document and cleanup drm_mode_config_funcs
  drm: document drm_mode_set structure
  drm: remove unused fields in drm_connector and document the rest
  drm: add drm_encoder comments
  drm: add comments for drm_encoder_funcs
  drm: fix comments for drm_crtc struct
  drm: remove unused connector_count field from drm_display_mode