[Driver][Mips] Support mips64-linux-gnuabi64 / mips64el-linux-gnuabi64 target triples.

The patch fixes the bug #19869.
http://llvm.org/bugs/show_bug.cgi?id=19869

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@211619 91177308-0d34-0410-b5e6-96231b3b80d8