util/cbfstool: Include commonlib/helpers.h in common.h

This avoids re-declaring common macros like ARRAY_SIZE, MIN, MAX and
ALIGN. Also removes the issues around including both files in any
tool.

Also, fix comparison error in various files by replacing int with
size_t.

Change-Id: I06c763e5dd1bec97e8335499468bbdb016eb28e5
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/14978
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

util/cbfstool/rmodule.c

@@ -595,7 +595,7 @@ out:
 int rmodule_init(struct rmod_context *ctx, const struct buffer *elfin)
 {
 	struct parsed_elf *pelf;
-	int i;
+	size_t i;
 	int ret;
 
 	ret = -1;