soc/intel/apollolake: Add missing DRAM density constants

Add missing constants for DRAM density. This resolves boot issue,
because misconfigured density results in incorrect memory mapping.

Change-Id: I3bad911bf406bfc5677059490d0e89fcbf735b70
Signed-off-by: Andrey Petrov <andrey.petrov@intel.com>
Reviewed-on: https://review.coreboot.org/15059
Tested-by: build bot (Jenkins)
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>

src/soc/intel/apollolake/include/soc/meminit.h

@@ -62,7 +62,7 @@ enum {
 
 /* LPDDR4 module density in bits. */
 enum {
-	LP4_8Gb_DENSITY,
+	LP4_8Gb_DENSITY = 2,
 	LP4_12Gb_DESNITY,
 	LP4_16Gb_DENSITY,
 };