{src,util}: Use NULL instead of 0 for pointer

Change-Id: I75fa4577055f25dde0a8b1044c005bba72cabd92
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/26857
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/drivers/intel/fsp1_0/hob.c

@@ -167,7 +167,7 @@ void print_guid_type_attributes(void *Hobptr)
 void print_hob_type_structure(u16 Hobtype, void *Hoblistptr)
 {
 	u32 *Currenthob;
-	u32 *Nexthob = 0;
+	u32 *Nexthob = NULL;
 	u8  Lasthob = 0;
 	u32 Currenttype;
 	const char *Currenttypestr;