ACPI: Make FADT entries for RTC/CMOS architectural

For AMD, replace name RTC_ALT_CENTURY with RTC_CLK_ALTCENTURY
that points to same offset. Since the century field inside
RTC falls within the NVRAM space, and could interfere with
OPTION_TABLE, it is now guarded with config USE_PC_CMOS_ALTCENTURY.

There were no reference for the use of offset 0x48 for century.

Change-Id: I965a83dc8daaa02ad0935bdde5ca50110adb014a
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/74601
Reviewed-by: Elyes Haouas <ehaouas@noos.fr>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>

src/acpi/acpi.c

@@ -1748,9 +1748,6 @@ static void acpi_create_fadt(acpi_fadt_t *fadt, acpi_facs_t *facs, void *dsdt)
 
 	fadt->preferred_pm_profile = acpi_get_preferred_pm_profile();
 
-	if (CONFIG(USE_PC_CMOS_ALTCENTURY))
-		fadt->century = RTC_CLK_ALTCENTURY;
-
 	fadt->sci_int = acpi_sci_int();
 
 	arch_fill_fadt(fadt);