Revert r215359 - [mips] Implement .ent, .end, .frame, .mask and .fmask assembler directives

It seems to cause an lld test (elf/Mips/hilo16-3.test) to fail. Reverted while we investigate.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215361 91177308-0d34-0410-b5e6-96231b3b80d8