[Mips] Do not adjust float-abi flags in case of MIPS16 mode. This code
should be isolated in the backend (r195123). From the frontend point
of view in case of "-mhard-float -mips16" combination of flags the float
ABI mode should remain unchanged.

The patch reviewed by Reed Kotler.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@195124 91177308-0d34-0410-b5e6-96231b3b80d8