Revert r304929 [mips] Add runtime options to enable/disable madd/sub.fmt

Revert r304929 since the test broke buildbots.

Original commit:

  [mips] Add runtime options to enable/disable madd.fmt and msub.fmt

  Add options to clang: -mmadd4 and -mno-madd4, use it to enable or disable
  generation of madd.fmt and similar instructions respectively, as per GCC.

  Patch by Stefan Maksimovic.

llvm-svn: 304935