Fix -Werror on 64-bit builds

Add another static_cast to avoid an error on 64-bit builds

Change-Id: I62fb2c67766c4aab70d9d1834f255d06ff82dd8d
(cherry picked from commit 116c7a113cb2db4d3f7708627ac4713c7e92cd43)
diff --git a/libs/ui/GraphicBuffer.cpp b/libs/ui/GraphicBuffer.cpp
index 825baf4..425df38 100644
--- a/libs/ui/GraphicBuffer.cpp
+++ b/libs/ui/GraphicBuffer.cpp
@@ -116,7 +116,7 @@
 }
 
 status_t GraphicBuffer::initCheck() const {
-    return mInitCheck;
+    return static_cast<status_t>(mInitCheck);
 }
 
 void GraphicBuffer::dumpAllocationsToSystemLog()