x86/mtrr: Simplify mtrr_bp_init()

x86/mtrr: Simplify mtrr_bp_init()

In case of the generic cache interface being used (Intel CPUs or a
64-bit system), the initialization sequence of the boot CPU is more
complicated than necessary:

- check if MTRR enabled, if yes, call mtrr_bp_pat_init() which will
  disable caching, set the PAT MSR, and reenable caching

- call mtrr_cleanup(), in case that changed anything, call
  cache_cpu_init() doing the same caching disable/enable dance as
  above, but this time with setting the (modified) MTRR state (even
  if MTRR was disabled) AND setting the PAT MSR (again even with
  disabled MTRR)

The sequence can be simplified a lot while removing potential
inconsistencies:

- check if MTRR enabled, if yes, call mtrr_cleanup() and then
  cache_cpu_init()

This ensures to:

- no longer disable/enable caching more than once

- avoid to set MTRRs and/or the PAT MSR on the boot processor in case
  of MTRR cleanups even if MTRRs meant to be disabled

With that mtrr_bp_pat_init() can be removed.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20221102074713.21493-10-jgross@suse.com
Signed-off-by: Borislav Petkov <bp@suse.de>