efibootmgr: add missing break for 'u' case

Reviewed by:	imp, zlei
Reported by:	Coverity
CID:		1505695
Fixes:		9a79152994 ("efibootmgr: Add --efidev (-u) to dis...")
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D38747

usr.sbin/efibootmgr/efibootmgr.c

@@ -290,6 +290,7 @@ parse_args(int argc, char *argv[])
 		case 'u':
 			opts.find_dev = true;
 			opts.dev = strdup(optarg);
+			break;
 		case 'v':
 			opts.verbose = true;
 			break;