[mips] Removed IsVarArg from MipsISelLowering::analyzeCallOperands(). NFC.

Summary:
CCState objects already carry this information in their isVarArg() method.

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D6084


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221516 91177308-0d34-0410-b5e6-96231b3b80d8