Intel hardware allows the primary plane to be disabled independently of
the CRTC.  Provide custom primary plane handling to allow this.

v8:
 - Pin/unpin properly when clipping causes the primary plane to be
   disabled when it has previously been enabled.
 - s/drm_primary_helper_check_update/drm_plane_helper_check_update/
v7:
 - Clip primary plane to invisible when crtc is disabled since
   intel_crtc->config.pipe_src_{w,h} may be garbage otherwise.
 - Unpin old fb before pinning new one in the "just pin and
   return" case that is used when the crtc is disabled.
 - Don't treat implicit disabling of the primary plane (caused by
   clipping) the same way as explicit disabling (caused by fb=0).
   For implicit disables, we should leave the fb set and pinned,
   whereas for explicit disables we need to unpin the fb before
   primary->fb is cleared.
v6:
 - Pass rectangles to primary helper check function and get plane
   visibility back.
 - Wait for pending pageflips on primary plane update/disable.
 - Allow primary plane to be updated while the crtc is disabled (changes
   will take effect when the crtc is re-enabled if modeset passes -1
   for the fb id).
 - Drop WARN() if we try to disable the primary plane when it's
   already been disabled.  This will happen if the crtc gets disabled
   after the primary plane has already been disabled independently.
v5:
 - Use new drm_primary_helper_check_update() helper function to check
   setplane parameter validity.
 - Swap primary plane's pipe for pre-gen4 FBC (caught by Ville Syrjälä)
 - Cleanup primary plane properly on crtc init failure
v4:
 - Don't add a primary_plane field to intel_crtc; that was left over
   from a much earlier iteration of this patch series, but is no longer
   needed/used now that the DRM core primary plane support has been
   merged.
v3:
 - Provide gen-specific primary plane format lists (suggested by Daniel
   Vetter).
 - If the primary plane is already enabled, go ahead and just call the
   primary plane helper to do the update (suggested by Daniel Vetter).
 - Don't try to disable the primary plane on destruction; the DRM layer
   should have already taken care of this for us.
v2:
 - Unpin fb properly on primary plane disable
 - Provide an Intel-specific set of primary plane formats
 - Additional sanity checks on setplane (in line with the checks
   currently being done by the DRM core primary plane helper)
Reviewed-by: Chon Ming Lee <chon.ming.lee@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>