[mips] Check emitted code for llvm.bswap.i32 on MIPS16/MIPS64 and llvm.bswap.i64 on MIPS16.

While reviewing r204163, I noticed that the MIPS16 test only checked for a .ent
directive and didn't actually check the code emitted. Fixed this and added a
check for llvm.bswap.i32 on MIPS64 at the same time.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205177 91177308-0d34-0410-b5e6-96231b3b80d8