Add Triple::isMIPS()/isMIPS32()/isMIPS64(). NFC

There are quite a few if statements that enumerate all these cases. It gets
even worse in our fork of LLVM where we also have a Triple::cheri (which
is mips64 + CHERI instructions) and we had to update all if statements that
check for Triple::mips64 to also handle Triple::cheri. This patch helps to
reduce our diff to upstream and should also make some checks more readable.

Reviewed By: atanasyan

Differential Revision: https://reviews.llvm.org/D48548

llvm-svn: 335493
diff --git a/llvm/lib/Transforms/Instrumentation/EfficiencySanitizer.cpp b/llvm/lib/Transforms/Instrumentation/EfficiencySanitizer.cpp
index 64f561d..33f220a 100644
--- a/llvm/lib/Transforms/Instrumentation/EfficiencySanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/EfficiencySanitizer.cpp
@@ -537,7 +537,7 @@
 bool EfficiencySanitizer::initOnModule(Module &M) {
 
   Triple TargetTriple(M.getTargetTriple());
-  if (TargetTriple.getArch() == Triple::mips64 || TargetTriple.getArch() == Triple::mips64el)
+  if (TargetTriple.isMIPS64())
     ShadowParams = ShadowParams40;
   else
     ShadowParams = ShadowParams47;