Add vector VEOR instruction to the integrated ARM assembler.

BUG= https://bugs.chromium.org/p/nativeclient/issues/detail?id=4334
R=eholk@chromium.org, stichnot@chromium.org

Review URL: https://codereview.chromium.org/1655363002 .
diff --git a/src/IceTargetLoweringARM32.cpp b/src/IceTargetLoweringARM32.cpp
index 34069eb..815c41f 100644
--- a/src/IceTargetLoweringARM32.cpp
+++ b/src/IceTargetLoweringARM32.cpp
@@ -2989,6 +2989,7 @@
   }
   case InstArithmetic::Xor: {
     Variable *Src0R = Srcs.src0R(this);
+    assert(isIntegerType(DestTy));
     if (isVectorType(DestTy)) {
       Variable *Src1R = legalizeToReg(Src1);
       _veor(T, Src0R, Src1R);