ACPICA: Add support for FFH Opregion special context data

ACPICA commit fad527b6e76babc7527c41325bfbef6bd1a1132b

FFH(Fixed Function Hardware) Opregion is approved to be added in ACPI 6.5 via
code first approach [1]. It requires special context data similar to GPIO and
Generic Serial Bus as it needs to know platform specific offset and length.

Add support for the special context data needed by FFH Opregion.

FFH op_region enables advanced use of FFH on some architectures. For example,
it could be used to easily proxy AML code to architecture-specific behavior
(to ensure it is OS initiated)

Actual behavior of FFH is ofcourse architecture specific and depends on
the FFH bindings. The offset and length could have arch specific meaning
or usage.

Link: https://bugzilla.tianocore.org/show_bug.cgi?id=3598 # [1]
Link: https://github.com/acpica/acpica/commit/fad527b6


Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>