nb/intel/nehalem: Remove unused MRC_CACHE_SIZE

Change-Id: I5d00fb238be6399ea6e9f394d8f899b03b1d44cf
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38906
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/northbridge/intel/nehalem/Kconfig

@@ -58,10 +58,6 @@ config DCACHE_BSP_STACK_SIZE
 	  The amount of anticipated stack usage in CAR by bootblock and
 	  other stages.
 
-config MRC_CACHE_SIZE
-	hex
-	default 0x10000
-
 config MMCONF_BASE_ADDRESS
 	hex
 	default 0xe0000000