nb/intel/sandybridge: remove unused duplicate PCIEXBAR define X60BAR

Change-Id: Ie5a28ceb3d1b684b9c94dcae5b303a4dce75f273
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38011
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/northbridge/intel/sandybridge/sandybridge.h

@@ -65,7 +65,6 @@ enum platform_type {
 #define MCHBAR		0x48
 #define PCIEXBAR	0x60
 #define DMIBAR		0x68
-#define X60BAR		0x60
 
 #define GGC		0x50			/* GMCH Graphics Control */