nb/intel/x4x: Define and use default MMCONF_BASE_ADDRESS

Currently only one board uses this northbridge in coreboot but some
patches are pending to add more.

Change-Id: If035e442d1a23674667f46a07b44c4f2b81be48c
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/19650
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>

src/mainboard/gigabyte/ga-g41m-es2l/Kconfig

@@ -35,10 +35,6 @@ config BOARD_SPECIFIC_OPTIONS
 	select HAVE_CMOS_DEFAULT
 	select HAVE_ACPI_RESUME
 
-config MMCONF_BASE_ADDRESS
-	hex
-	default 0xe0000000
-
 config MAINBOARD_DIR
 	string
 	default "gigabyte/ga-g41m-es2l"

src/northbridge/intel/x4x/Kconfig

@@ -38,4 +38,8 @@ config VGA_BIOS_ID
 	string
 	default "8086,2e32"
 
+config MMCONF_BASE_ADDRESS
+	hex
+	default 0xe0000000
+
 endif