Fix ALIGNED misuse in asan_thread.cc (built on all platforms); also, add a comment to the ALIGNED macro describing the correct usage

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@183214 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/asan/asan_thread.cc b/lib/asan/asan_thread.cc
index 5018b75..1af3f74 100644
--- a/lib/asan/asan_thread.cc
+++ b/lib/asan/asan_thread.cc
@@ -40,7 +40,7 @@
 }
 
 // MIPS requires aligned address
-static char thread_registry_placeholder[sizeof(ThreadRegistry)] ALIGNED(16);
+static ALIGNED(16) char thread_registry_placeholder[sizeof(ThreadRegistry)];
 static ThreadRegistry *asan_thread_registry;
 
 static ThreadContextBase *GetAsanThreadContext(u32 tid) {