SurfaceControl: Remove setOverrideScalingMode

Following recent frameworks/base changes there are no callers.

Bug: 161937501
Test: Existing tests pass
Change-Id: I1a39d30ebd70a0b0cb430a6d1ae48086c3e1806e
diff --git a/services/surfaceflinger/BufferLayer.h b/services/surfaceflinger/BufferLayer.h
index 1cd753b..e6a0f81 100644
--- a/services/surfaceflinger/BufferLayer.h
+++ b/services/surfaceflinger/BufferLayer.h
@@ -94,8 +94,7 @@
 
     bool hasReadyFrame() const override;
 
-    // Returns the current scaling mode, unless mOverrideScalingMode
-    // is set, in which case, it returns mOverrideScalingMode
+    // Returns the current scaling mode
     uint32_t getEffectiveScalingMode() const override;
 
     // Calls latchBuffer if the buffer has a frame queued and then releases the buffer.