src: Make use of 'CEIL_DIV(a, b)' macro across tree

The objective here is to tighten coreboot up a bit by not repeating
common helpers. This makes the code base more consistent and
unified/tight.

Change-Id: Ia163eae68b4a84a00ed118125e70308fab1cea0c
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/6215
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/northbridge/intel/gm45/raminit.c

@@ -362,7 +362,7 @@ static void collect_ddr3(spdinfo_t *const config)
 	}
 }
 
-#define ROUNDUP_DIV(val, by) (((val) + (by) - 1) / (by))
+#define ROUNDUP_DIV(val, by) CEIL_DIV(val, by)
 #define ROUNDUP_DIV_THIS(val, by) val = ROUNDUP_DIV(val, by)
 static fsb_clock_t read_fsb_clock(void)
 {