nb/intel/x4x: Correct and use macros for CLKCFG

The `CLKCFG_UPDATE` macro is copied from gm45 and unused. Correct it and
use the CLKCFG macros instead of magic values.

Tested with BUILD_TIMELESS=1, Asus P5QL PRO remains identical.

Change-Id: I17e972eba21282ac84c7afe10b7149cd1131fd07
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/51877
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/northbridge/intel/x4x/early_init.c b/src/northbridge/intel/x4x/early_init.c
index f942d59..e6083d9 100644
--- a/src/northbridge/intel/x4x/early_init.c
+++ b/src/northbridge/intel/x4x/early_init.c
@@ -62,7 +62,7 @@
 	EPBAR8(EPVC0RCTL) = 1;
 	EPBAR8(EPPVCCAP1) = 1;
 
-	switch (MCHBAR32(0xc00) & 0x7) {
+	switch (MCHBAR32(CLKCFG_MCHBAR) & CLKCFG_FSBCLK_MASK) {
 	case 0x0:
 		/* FSB 1066 */
 		EPBAR32(EPVC1ITC) = 0x0001a6db;