Update aosp/master LLVM for rebase to r222494.

Change-Id: Ic787f5e0124df789bd26f3f24680f45e678eef2d
diff --git a/lib/CodeGen/RegAllocBasic.cpp b/lib/CodeGen/RegAllocBasic.cpp
index b722098..0090332 100644
--- a/lib/CodeGen/RegAllocBasic.cpp
+++ b/lib/CodeGen/RegAllocBasic.cpp
@@ -33,7 +33,6 @@
 #include "llvm/PassAnalysisSupport.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
-#include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetRegisterInfo.h"
 #include <cstdlib>
 #include <queue>
@@ -157,7 +156,7 @@
 }
 
 void RABasic::releaseMemory() {
-  SpillerInstance.reset(nullptr);
+  SpillerInstance.reset();
 }