drm/i915: Calculate haswell plane workaround, v5.

This needs to be done last after all modesets have been calculated.

A modeset first disables all crtc's, so any crtc that undergoes a
modeset counts as inactive.

If no modeset's done, or > 1 crtc's stay w/a doesn't apply.
Apply workaround on the first crtc if 1 crtc stays active.
Apply workaround on the second crtc if no crtc was active.

Changes since v1:
 - Use intel_crtc->atomic as a place to put hsw_workaround_pipe.
 - Make sure quirk only applies to haswell.
 - Use first loop to iterate over newly enabled crtc's only.
   This increases readability.
Changes since v2:
 - Move hsw_workaround_pipe back to crtc_state.
Changes since v3:
 - Return errors from haswell_mode_set_planes_workaround.
Changes since v4:
- Clean up commit message.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 6d9c771..5312160 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -443,6 +443,9 @@
 	int pbn;
 
 	struct intel_crtc_scaler_state scaler_state;
+
+	/* w/a for waiting 2 vblanks during crtc enable */
+	enum pipe hsw_workaround_pipe;
 };
 
 struct intel_pipe_wm {