arm64: FFH: Move ACPI specific code into drivers/acpi/arm64/

The ACPI FFH Opregion code can be moved out of arm64 arch code as
it just uses SMCCC. Move all the ACPI FFH Opregion code into
drivers/acpi/arm64/ffh.c

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Hanjun Guo <guohanjun@huawei.com>
Link: https://lore.kernel.org/r/20240605131458.3341095-4-sudeep.holla@arm.com


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>