[mips] Some uses of isMips64()/hasMips64() are really tests for 64-bit GPR's

Summary:
No functional change since these predicates are (currently) synonymous.

Extracted from a patch by David Chisnall
His work was sponsored by: DARPA, AFRL

Differential Revision: http://llvm-reviews.chandlerc.com/D3202

llvm-svn: 204943
diff --git a/llvm/lib/Target/Mips/MipsISelLowering.cpp b/llvm/lib/Target/Mips/MipsISelLowering.cpp
index 13de7e3..11eee42 100644
--- a/llvm/lib/Target/Mips/MipsISelLowering.cpp
+++ b/llvm/lib/Target/Mips/MipsISelLowering.cpp
@@ -3029,9 +3029,9 @@
           return std::make_pair(0U, &Mips::CPU16RegsRegClass);
         return std::make_pair(0U, &Mips::GPR32RegClass);
       }
-      if (VT == MVT::i64 && !hasMips64())
+      if (VT == MVT::i64 && !isGP64bit())
         return std::make_pair(0U, &Mips::GPR32RegClass);
-      if (VT == MVT::i64 && hasMips64())
+      if (VT == MVT::i64 && isGP64bit())
         return std::make_pair(0U, &Mips::GPR64RegClass);
       // This will generate an error message
       return std::make_pair(0u, static_cast<const TargetRegisterClass*>(0));