drm/i915: Add a timing breadcrumb to panel waits

When inspecting reports that boot/suspend/resume times are unusual it
would be useful to clearly identify the time we must spend waiting for
the hardware to complete its task. In this case we have a notification
before we start waiting for the panel to change state, but none
afterwards - which would be useful.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_dp.c

@@ -1037,6 +1037,8 @@ static void ironlake_wait_panel_status(struct intel_dp *intel_dp,
 				I915_READ(pp_stat_reg),
 				I915_READ(pp_ctrl_reg));
 	}
+
+	DRM_DEBUG_KMS("Wait complete\n");
 }
 
 static void ironlake_wait_panel_on(struct intel_dp *intel_dp)