ip link: Add group in usage() for 'ip link delete'

Show deleting by group in 'ip link help' output:

...
ip link delete { DEVICE | dev DEVICE | group DEVGROUP } type TYPE [ ARGS ]
...

Also show separately DEVICE option in { } list.
Signed-off-by: Vadim Kochan <vadim4j@gmail.com>

ip/iplink.c

@@ -53,9 +53,9 @@ void iplink_usage(void)
 		fprintf(stderr, "                   [ numtxqueues QUEUE_COUNT ]\n");
 		fprintf(stderr, "                   [ numrxqueues QUEUE_COUNT ]\n");
 		fprintf(stderr, "                   type TYPE [ ARGS ]\n");
-		fprintf(stderr, "       ip link delete DEV type TYPE [ ARGS ]\n");
+		fprintf(stderr, "       ip link delete { DEVICE | dev DEVICE | group DEVGROUP } type TYPE [ ARGS ]\n");
 		fprintf(stderr, "\n");
-		fprintf(stderr, "       ip link set { dev DEVICE | group DEVGROUP } [ { up | down } ]\n");
+		fprintf(stderr, "       ip link set { DEVICE | dev DEVICE | group DEVGROUP } [ { up | down } ]\n");
 	} else
 		fprintf(stderr, "Usage: ip link set DEVICE [ { up | down } ]\n");