nb/intel/sandybridge/romstage: Use register name

Use register name instead of hex value.
No functional change.

Change-Id: Iacfe609f6454e6d58c9733f425377464238ce4a9
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/19544
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Sumeet R Pawnikar <sumeet.r.pawnikar@intel.com>

src/northbridge/intel/sandybridge/romstage.c

@@ -38,9 +38,9 @@ static void early_pch_init(void)
 	u8 reg8;
 
 	// reset rtc power status
-	reg8 = pci_read_config8(PCH_LPC_DEV, 0xa4);
+	reg8 = pci_read_config8(PCH_LPC_DEV, GEN_PMCON_3);
 	reg8 &= ~(1 << 2);
-	pci_write_config8(PCH_LPC_DEV, 0xa4, reg8);
+	pci_write_config8(PCH_LPC_DEV, GEN_PMCON_3, reg8);
 }
 
 /* Platform has no romstage entry point under mainboard directory,