util/msrtool: Exit program after displaying the help message

In case there is no mode selected, sys and cpu variables are not
initialized, causing a segfault on exit (goto done).

Change-Id: I4a183c267e306598627c1612f4633f1e19019f3c
Signed-off-by: Maciej Suminski <maciej.suminski@cern.ch>
Reviewed-on: https://review.coreboot.org/21026
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Pratikkumar V Prajapati <pratikkumar.v.prajapati@intel.com>

util/msrtool/msrtool.c

@@ -417,7 +417,7 @@ int main(int argc, char *argv[]) {
 	if (optind == argc) {
 		syntax(argv);
 		printf("\nNo mode or address(es) specified!\n");
-		goto done;
+		return 1;
 	}
 
 	if (!found_system())