[mips] Pass ABI name via -target-abi instead of target-features

Patch by Vladimir Medic

Reviewers: echristo, atanasyan, dsanders

Reviewed By: atanasyan, dsanders

Subscribers: llvm-commits, echristo, atanasyan

Differential Revision: http://reviews.llvm.org/D6091

llvm-svn: 227583