drm/i915/dp: Make sure all tiled connectors get added to the state with full modeset

In case of tiled displays, all the tiles are linke dto each other
for transcoder port sync. So in intel_atomic_check() we need to make
sure that we add all the tiles to the modeset and if one of the
tiles needs a full modeset then mark all other tiles for a full modeset.

We also need to force modeset for all synced crtcs after fastset check.

v6:
* Add comments about why we do not call
drm_atomic_helper_check_modeset (Matt)
* Add FIXME for a corner case where tile info might vanish (Matt)
v5:
* Rebase
v4:
* Fix logic for modeset_synced_crtcs (Ville)
v3:
* Add tile checks only for Gen >11
v2:
* Change crtc_state scope, remove tile_grp_id (Ville)
* Use intel_connector_needs_modeset() (Ville)
* Add modeset_synced_crtcs (Ville)
* Make sure synced crtcs are forced full modeset
after fastset check (Ville)

Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Bugzilla: https://gitlab.freedesktop.org/drm/intel/issues/5
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191228031204.10189-1-manasi.d.navare@intel.com