Some Asus AMD systems are reported to not be able to change EPP values
because the BIOS doesn't advertise support for the CPPC MSR and the PCC
region is not configured.

However the ACPI 6.2 specification allows CPC registers to be declared
in FFH:
```
Starting with ACPI Specification 6.2, all _CPC registers can be in
PCC, System Memory, System IO, or Functional Fixed Hardware address
spaces. OSPM support for this more flexible register space scheme
is indicated by the “Flexible Address Space for CPPC Registers” _OSC
bit.
```

If this _OSC has been set allow using FFH to configure EPP.

Reported-by: al0uette@outlook.com
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218686
Suggested-by: al0uette@outlook.com
Tested-by: vderp@icloud.com
Tested-by: al0uette@outlook.com
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://patch.msgid.link/20240910031524.106387-1-superm1@kernel.orgSigned-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>