iproute: TYPE keyword is not optional, fix help text accordingly

This is a bit pedantic, but brackets ([]) show optional values and since
TYPE must not become empty, they're not suited to surround the type
keyword choices. Use curly braces instead.

Also add some missing whitespace to the parameter list above.
Signed-off-by: Phil Sutter <phil@nwl.cc>

ip/iproute.c

@@ -82,13 +82,13 @@ static void usage(void)
 	fprintf(stderr, "FAMILY := [ inet | inet6 | ipx | dnet | mpls | bridge | link ]\n");
 	fprintf(stderr, "OPTIONS := FLAGS [ mtu NUMBER ] [ advmss NUMBER ] [ as [ to ] ADDRESS ]\n");
 	fprintf(stderr, "           [ rtt TIME ] [ rttvar TIME ] [ reordering NUMBER ]\n");
-	fprintf(stderr, "           [ window NUMBER] [ cwnd NUMBER ] [ initcwnd NUMBER ]\n");
+	fprintf(stderr, "           [ window NUMBER ] [ cwnd NUMBER ] [ initcwnd NUMBER ]\n");
 	fprintf(stderr, "           [ ssthresh NUMBER ] [ realms REALM ] [ src ADDRESS ]\n");
 	fprintf(stderr, "           [ rto_min TIME ] [ hoplimit NUMBER ] [ initrwnd NUMBER ]\n");
 	fprintf(stderr, "           [ features FEATURES ] [ quickack BOOL ] [ congctl NAME ]\n");
 	fprintf(stderr, "           [ pref PREF ] [ expires TIME ]\n");
-	fprintf(stderr, "TYPE := [ unicast | local | broadcast | multicast | throw |\n");
-	fprintf(stderr, "          unreachable | prohibit | blackhole | nat ]\n");
+	fprintf(stderr, "TYPE := { unicast | local | broadcast | multicast | throw |\n");
+	fprintf(stderr, "          unreachable | prohibit | blackhole | nat }\n");
 	fprintf(stderr, "TABLE_ID := [ local | main | default | all | NUMBER ]\n");
 	fprintf(stderr, "SCOPE := [ host | link | global | NUMBER ]\n");
 	fprintf(stderr, "NHFLAGS := [ onlink | pervasive ]\n");