Reduce number of copies into unmapExternalTextureBuffer

Make unmapExternalTextureBuffer take in an rvalue of sp<GraphicBuffer>,
which reduces the number sp copies.

Bug: 215661436
Test: builds
Change-Id: I4f9b6e3d6863ce6815810fdda038dc9e730f0b44
diff --git a/libs/renderengine/skia/SkiaRenderEngine.cpp b/libs/renderengine/skia/SkiaRenderEngine.cpp
index 413811e..5965d41 100644
--- a/libs/renderengine/skia/SkiaRenderEngine.cpp
+++ b/libs/renderengine/skia/SkiaRenderEngine.cpp
@@ -423,7 +423,7 @@
     }
 }
 
-void SkiaRenderEngine::unmapExternalTextureBuffer(const sp<GraphicBuffer>& buffer) {
+void SkiaRenderEngine::unmapExternalTextureBuffer(sp<GraphicBuffer>&& buffer) {
     ATRACE_CALL();
     std::lock_guard<std::mutex> lock(mRenderingMutex);
     if (const auto& iter = mGraphicBufferExternalRefs.find(buffer->getId());