soc/amd/common/block/acpi/cpu_power_state: use definition for bit_offset

Instead of using a magic constant in the bit_offset field of the C state
resource for the C1 state that's entered via the MWAIT instruction, use
the existing ACPI_FFIXEDHW_CLASS_MWAIT define. This value is checked by
acpi_processor_ffh_cstate_probe in the Linux kernel.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: I9edc681efab15b5ceba91c8105f7dc6d687d8be8
Reviewed-on: https://review.coreboot.org/c/coreboot/+/73498
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Reviewed-by: Fred Reitberger <reitbergerfred@gmail.com>

src/soc/amd/common/block/acpi/cpu_power_state.c

@@ -24,7 +24,7 @@ static void write_cstate_entry(acpi_cstate_t *entry, const acpi_cstate_t *data,
 		entry->resource = (acpi_addr_t){
 			.space_id = ACPI_ADDRESS_SPACE_FIXED,
 			.bit_width = 2,
-			.bit_offset = 2,
+			.bit_offset = ACPI_FFIXEDHW_CLASS_MWAIT,
 			.addrl = 0,
 			.addrh = 0,
 		};