iproute2: revert syntax help text mistake.

Sorry. The pref and prio options are actually synonyms.
This reverts part of commit 576c63ee.
Signed-off-by: Andreas Henriksson <andreas@fatal.se>
Signed-off-by: Stephen Hemminger <stephen.hemminger@vyatta.com>

ip/iprule.c

@@ -38,7 +38,7 @@ static void usage(void)
 {
 	fprintf(stderr, "Usage: ip rule [ list | add | del | flush ] SELECTOR ACTION\n");
 	fprintf(stderr, "SELECTOR := [ not ] [ from PREFIX ] [ to PREFIX ] [ tos TOS ] [ fwmark FWMARK[/MASK] ]\n");
-	fprintf(stderr, "            [ dev STRING ] [ pref NUMBER ] [ prio NUMBER ]\n");
+	fprintf(stderr, "            [ dev STRING ] [ pref NUMBER ]\n");
 	fprintf(stderr, "ACTION := [ table TABLE_ID ]\n");
 	fprintf(stderr, "          [ prohibit | reject | unreachable ]\n");
 	fprintf(stderr, "          [ realms [SRCREALM/]DSTREALM ]\n");