ACPI: PCC: Add PCC shared memory region command and status bitfields

Define the common macros to use when referring to various bitfields in
the PCC generic communications channel command and status fields.

Currently different drivers that need to use these bitfields have defined
these locally. This common macro is intended to consolidate and replace
those.

Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20230927-pcc_defines-v2-1-0b8ffeaef2e5@arm.com


Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>