Layer: Don't need atomic for transaction flags

Following queued transaction changes we don't need an atomic here
since setPosition etc all execute on the main thread.

Test: Existing tests pass. simpleperf
Bug: 186200583
Change-Id: I965d3883d30ce1eb3c452742535281f3e2719424
diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index 2bf5602..00defb3 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -847,11 +847,13 @@
 }
 
 uint32_t Layer::getTransactionFlags(uint32_t flags) {
-    return mTransactionFlags.fetch_and(~flags) & flags;
+    auto ret = mTransactionFlags & flags;
+    mTransactionFlags &= ~flags;
+    return ret;
 }
 
 uint32_t Layer::setTransactionFlags(uint32_t flags) {
-    return mTransactionFlags.fetch_or(flags);
+    return mTransactionFlags |= flags;
 }
 
 bool Layer::setPosition(float x, float y) {