SF: Remove fallback for outdated active display

Initialize mActiveDisplayId during boot. getDefaultDisplay's fallback is
then no longer needed, since mActiveDisplayId is an internal display, so
cannot be removed and become outdated.

Bug: 255635821
Flag: EXEMPT refactor
Test: Boot
Change-Id: Ifa1a1f679957e88788b1819ba117fda3f407430b
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 22a8993..216fb43 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -911,9 +911,11 @@
     LOG_ALWAYS_FATAL_IF(!configureLocked(),
                         "Initial display configuration failed: HWC did not hotplug");
 
+    mActiveDisplayId = getPrimaryDisplayIdLocked();
+
     // Commit primary display.
     sp<const DisplayDevice> display;
-    if (const auto indexOpt = mCurrentState.getDisplayIndex(getPrimaryDisplayIdLocked())) {
+    if (const auto indexOpt = mCurrentState.getDisplayIndex(mActiveDisplayId)) {
         const auto& displays = mCurrentState.displays;
 
         const auto& token = displays.keyAt(*indexOpt);