This is the 1st patch in the series. Here the aim was to avoid any
significant changes, logically-wise.
So it's mainly about generic interface refactoring: e.g. make
microcode_{intel,amd}.c more about arch-specific details and less
about policies like make-sure-we-run-on-a-target-cpu
(no more set_cpus_allowed_ptr() here) and generic synchronization (no
more microcode_mutex here).
All in all, more line have been deleted than added.