base-files: make wifi report unknown command

Avoid having /sbin/wifi silently ignore unknown keywords and execute
"up"; instead display the help message and exit with an error.

Spell out the "up" keyword (which has users), add it to usage output,
and preserve the implicit assumption that runing /sbin/wifi without
argument performs "up".

Signed-off-by: Thibaut VARÈNE <hacks@slashdirt.org>

package/base-files/files/sbin/wifi

@@ -6,7 +6,7 @@
 
 usage() {
 	cat <<EOF
-Usage: $0 [config|down|reload|status]
+Usage: $0 [config|up|down|reload|status]
 enables (default), disables or configures devices not yet configured.
 EOF
 	exit 1
@@ -241,5 +241,6 @@ case "$1" in
 	reload) wifi_reload "$2";;
 	reload_legacy) wifi_reload_legacy "$2";;
 	--help|help) usage;;
-	*) ubus call network reload; wifi_updown "enable" "$2";;
+	''|up) ubus call network reload; wifi_updown "enable" "$2";;
+	*) usage; exit 1;;
 esac