ACPI: Remove Kconfig COMMON_FADT

Also remove default mb/*/fadt.c from Makefiles.

Change-Id: I6a2839c524f8311ec9a382a84066afc7d579eaca
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41948
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/baytrail/Kconfig

@@ -14,7 +14,6 @@ config CPU_SPECIFIC_OPTIONS
 	select ARCH_RAMSTAGE_X86_32
 	select BOOT_DEVICE_SUPPORTS_WRITES
 	select CACHE_MRC_SETTINGS
-	select COMMON_FADT
 	select CPU_INTEL_TURBO_NOT_PACKAGE_SCOPED
 	select SUPPORT_CPU_UCODE_IN_CBFS
 	select HAVE_SMI_HANDLER