[Mips] Remove unused mips_CPUs_Group options group. It's better to join
all MIPS-related options to the new m_mips_Features_Group later.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@192291 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed