net: mctp: remove redundant RTN_UNICAST check

Current mctp_newroute() contains two exactly same check against
rtm->rtm_type

static int mctp_newroute(...)
{
...
    if (rtm->rtm_type != RTN_UNICAST) { // (1)
        NL_SET_ERR_MSG(extack, "rtm_type must be RTN_UNICAST");
        return -EINVAL;
    }
...
    if (rtm->rtm_type != RTN_UNICAST) // (2)
        return -EINVAL;
...
}

This commits removes the (2) check as it is redundant.
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Reviewed-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Acked-by: Jeremy Kerr <jk@codeconstruct.com.au>
Link: https://lore.kernel.org/r/20230615152240.1749428-1-linma@zju.edu.cnSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/mctp/route.c

@@ -1249,9 +1249,6 @@ static int mctp_newroute(struct sk_buff *skb, struct nlmsghdr *nlh,
 			mtu = nla_get_u32(tbx[RTAX_MTU]);
 	}
 
-	if (rtm->rtm_type != RTN_UNICAST)
-		return -EINVAL;
-
 	rc = mctp_route_add(mdev, daddr_start, rtm->rtm_dst_len, mtu,
 			    rtm->rtm_type);
 	return rc;