[mips] Generate tests expectations using update_llc_test_checks. NFC

Generate tests expectations using update_llc_test_checks and reduce
number of "check prefixes" used in the tests.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@343485 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed