nb/intel/sandybridge/raminit: Allow 933Mhz on Lenovo devices

Set max_mem_clock_mhz in devicetree to 933Mhz.
Allows to run the memory at up to DDR3-1866.

The same frequency was allowed within the first vendor bios,
but Lenovo than decided to limit it to DDR3-1333.

Tested on Lenovo T520 and DDR3-1600 DIMM (RMT3170eb86e9w16).

The RAM is now running at DDR3-1600 instead of DDR3-1333.
This gives about 4% performance increase in glmark2 using the
Intel GPU.

Change-Id: If15be497402d84a2778f0434b6381a64eda832d6
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/15158
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Martin Roth <martinroth@google.com>
diff --git a/src/northbridge/intel/sandybridge/raminit.c b/src/northbridge/intel/sandybridge/raminit.c
index 4563547..15590d1 100644
--- a/src/northbridge/intel/sandybridge/raminit.c
+++ b/src/northbridge/intel/sandybridge/raminit.c
@@ -4374,7 +4374,11 @@
 		}
 		return DEFAULT_TCK;
 	} else {
-		if (cfg->max_mem_clock_mhz >= 800)
+		if (cfg->max_mem_clock_mhz >= 1066)
+			return TCK_1066MHZ;
+		else if (cfg->max_mem_clock_mhz >= 933)
+			return TCK_933MHZ;
+		else if (cfg->max_mem_clock_mhz >= 800)
 			return TCK_800MHZ;
 		else if (cfg->max_mem_clock_mhz >= 666)
 			return TCK_666MHZ;