SF: Deduplicate state for active display mode

RefreshRateConfigs tracks the active mode, so remove the duplicate (and
not thread-safe) state in DisplayDevice.

Bug: 241285191
Test: Build (-Wthread-safety)
Change-Id: I6b551cc68da3916a797a28085be984667fa1901e
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 1f8874d..fdaacf0 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -1340,7 +1340,7 @@
 
     std::unique_ptr<Hwc2::PowerAdvisor> mPowerAdvisor;
 
-    void enableRefreshRateOverlay(bool enable) REQUIRES(mStateLock);
+    void enableRefreshRateOverlay(bool enable) REQUIRES(mStateLock, kMainThreadContext);
 
     // Flag used to set override desired display mode from backdoor
     bool mDebugDisplayModeSetByBackdoor = false;