acpi: Add SSDT pstate helper functions

acpi: Add SSDT pstate helper functions

Add new generic helper functions for PSS, PCT, XPSS, objects.

BUG=b:155307433
TEST=Boot Morphius and dump SSDT. Confirm PSS and PCT objects appear
as expected and conform to ACPI_6_3_May16.pdf ACPI specification.
Check XPSS against Microsoft "Extended PSS ACPI Method Specification"
XPSS_spec.doc April 2, 2007.
BRANCH=Zork

Change-Id: I1ea218bcee33093481e82390550ff96d9d2cb8b5
Signed-off-by: Jason Glenesk <jason.glenesk@amd.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/45437
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>