Update LLVM for rebase to r212749.

Includes a cherry-pick of:
r212948 - fixes a small issue with atomic calls

Change-Id: Ib97bd980b59f18142a69506400911a6009d9df18
diff --git a/lib/Target/ARM/ARMMCInstLower.cpp b/lib/Target/ARM/ARMMCInstLower.cpp
index 48141b1..023f5f8 100644
--- a/lib/Target/ARM/ARMMCInstLower.cpp
+++ b/lib/Target/ARM/ARMMCInstLower.cpp
@@ -34,7 +34,7 @@
                                    OutContext);
     switch (Option) {
     default: llvm_unreachable("Unknown target flag on symbol operand");
-    case 0:
+    case ARMII::MO_NO_FLAG:
       break;
     case ARMII::MO_LO16:
       Expr = MCSymbolRefExpr::Create(Symbol, MCSymbolRefExpr::VK_None,