Comment 2 for bug 1791080

Continue Spectre v4 review:
* x86/speculation: Update Speculation Control microcode
  blacklist
  -> skip, we do not carry the blacklist
* x86/speculation: Correct Speculation Control
  microcode blacklist again
  -> skip, again firmware blacklist
* x86/speculation: Clean up various Spectre related
  details
  -> pick, adjusted to match intended goals (low risk
     as this is only removing line breaks or updating
     printks).
* x86/speculation: Add <asm/msr-index.h> dependency
  -> skip, no change
* x86/spectre_v2: Don't check microcode versions when
  running under hypervisors
  -> skip, we do not check for bad microcode versions
* x86/speculation: Use IBRS if available before calling
  into firmware
  -> pick, adapted to current environment. We already
     had alternative_msr_write() ported.