[mips][ias] Work around yet another incorrect microMIPS relocation evaluation exposed by r268900.

It's not entirely clear why R_MICROMIPS_(GOT|HI16|LO16) are evaluated
incorrectly in a small number of the LNT tests at this point. However, it's not
related to the STO_MIPS_MICROMIPS issue.

At this point all the microMIPS-related changes of r268900 have been reverted.

llvm-svn: 269410