nb/intel/sandybridge: Use 133 MHz ref clock for DDR3-2400

The 100 MHz reference clock seems to be unstable when using high
multipliers. Use the 133 MHz reference clock instead.

Change-Id: I400e4f91776306d54d818fa249d7a845020ac37b
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/45503
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/northbridge/intel/sandybridge/raminit_native.c

@@ -218,7 +218,7 @@ static void normalize_tclk(ramctr_timing *ctrl, bool ref_100mhz_support)
 {
 	if (ctrl->tCK <= TCK_1200MHZ) {
 		ctrl->tCK = TCK_1200MHZ;
-		ctrl->base_freq = 100;
+		ctrl->base_freq = 133;
 	} else if (ctrl->tCK <= TCK_1100MHZ) {
 		ctrl->tCK = TCK_1100MHZ;
 		ctrl->base_freq = 100;