nb/intel/sandybridge: Fix mrc.bin path

The mrc.bin uses a lot of stack. The BSP stack size is kept
the same for both romstage bootpaths, mrc.bin and native,
in order for the CAR symbol/setups to be compatible.

Change-Id: Ic422980ca1a0549b6937e30a433ce52e0d7a595c
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37185
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/northbridge/intel/sandybridge/Kconfig

@@ -74,7 +74,10 @@ config DCACHE_RAM_BASE
 
 config DCACHE_BSP_STACK_SIZE
 	hex
-	default 0x2800
+	default 0x10000
+	help
+	  The amount of BSP stack anticipated in bootblock and
+	  other stages.
 
 if USE_NATIVE_RAMINIT