nb/intel/i945: Use UPMC4 macro

Change-Id: Id3fb39edb0f14d48b9ea84b882fc46790fc37524
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50632
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/northbridge/intel/i945/raminit.c

@@ -2286,10 +2286,10 @@ static void sdram_power_management(struct sys_info *sysinfo)
 
 	MCHBAR32(PMCFG) |= (1 << 4);
 
-	reg32 = MCHBAR32(0xc30);
+	reg32 = MCHBAR32(UPMC4);
 	reg32 &= 0xffffff00;
 	reg32 |= 0x01;
-	MCHBAR32(0xc30) = reg32;
+	MCHBAR32(UPMC4) = reg32;
 
 	MCHBAR32(0xb18) &= ~(1 << 21);
 }