[x86] regenerate checks with update_llc_test_checks.py

The dream of a unified check-line auto-generator for all phases of compilation is dead.
The llc script has already diverged to be better at its goal, so having 2 scripts that
do almost the same thing is just causing confusion.

We can rip out the llc ability in update_test_checks.py next and rename it, so it will
be clear that we have one script for llc check auto-generation and another for opt.

llvm-svn: 305206