nb/intel/sandybridge/raminit: Add Kconfig option for fuses

Add a new Kconfig option to ignore memory fuses that limit the
maximum DRAM frequency to be used. The option is disabled by
default and should only enabled by experienced users as it
might decrease system stability or prevent a successful RAM
training.

Remove conflicting devicetree settings.

Change-Id: I35dd78a02bcaafce8ba522d253c795d7835bacae
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/20907
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Nicola Corna <nicola@corna.info>
diff --git a/src/northbridge/intel/sandybridge/Kconfig b/src/northbridge/intel/sandybridge/Kconfig
index 2d13f28..7c954fb 100644
--- a/src/northbridge/intel/sandybridge/Kconfig
+++ b/src/northbridge/intel/sandybridge/Kconfig
@@ -44,6 +44,18 @@
 	  Select if you want to use coreboot implementation of raminit rather than
 	  System Agent/MRC.bin. You should answer Y.
 
+config NATIVE_RAMINIT_IGNORE_MAX_MEM_FUSES
+	bool "Ignore vendor programmed fuses that limit max. DRAM frequency"
+	default n
+	depends on USE_NATIVE_RAMINIT
+	help
+	  Ignore the mainboard's vendor programmed fuses that might limit the
+	  maximum DRAM frequency. By selecting this option the fuses will be
+	  ignored and the only limits on DRAM frequency are set by RAM's SPD and
+	  hard fuses in southbridge's clockgen.
+	  Disabled by default as it might causes system instability.
+	  Handle with care!
+
 config CBFS_SIZE
 	hex
 	default 0x100000