[utils][mips] Add support for mips for update_llc_checks.py

Add support for mips, particularly skipping the matching of .frame, .(f)mask
and LLVM's usage of the .set no(reorder|at|macro) directives.

Reviewers: spatel

Differential Revision: https://reviews.llvm.org/D40268

llvm-svn: 319001