tools: mkfwumdata: Improve error message specificity

Replace the generic error message with a more informative one.
This helps users quickly understand the correct command-line argument
format when the tool reports an error.

Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
Tested-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

tools/fwumdata_src/mkfwumdata.c

@@ -473,7 +473,9 @@ int main(int argc, char *argv[])
 
 	/* This command takes UUIDs * images and output file. */
 	if (optind + images + 1 != argc) {
-		fprintf(stderr, "Error: UUID list or output file is not specified or too much.\n");
+		fprintf(stderr,
+			"Error: Expected %ld UUID string(s) and 1 output file, got %d argument(s).\n",
+			images, argc - optind);
 		print_usage();
 		return -ERANGE;
 	}