[mips] Remove ByValArgInfo::Address in favour of CCValAssign::getMemLocOffset(). NFC.

Summary: ByValArgInfo is practically the same as CCState::ByValInfo now.

Reviewers: vmedic

Reviewed By: vmedic

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D5976

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221057 91177308-0d34-0410-b5e6-96231b3b80d8