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/icelake/Kconfig

@@ -15,7 +15,6 @@ config CPU_SPECIFIC_OPTIONS
 	select BOOT_DEVICE_SPI_FLASH_RW_NOMMAP_EARLY if BOOT_DEVICE_SPI_FLASH
 	select BOOT_DEVICE_SUPPORTS_WRITES
 	select CACHE_MRC_SETTINGS
-	select COMMON_FADT
 	select CPU_INTEL_FIRMWARE_INTERFACE_TABLE
 	select FSP_M_XIP
 	select GENERIC_GPIO_LIB