sctp: sm_statefuns: Remove pointer casts of the same type

The subh.addip_hdr pointer is also of type (struct sctp_addiphdr *), so
it does not require a cast.
Signed-off-by: Li zeming <zeming@nfschina.com>
Link: https://lore.kernel.org/r/20221115020705.3220-1-zeming@nfschina.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>

net/sctp/sm_statefuns.c

@@ -4044,7 +4044,7 @@ enum sctp_disposition sctp_sf_do_asconf_ack(struct net *net,
 			   (void *)err_param, commands);
 
 	if (last_asconf) {
-		addip_hdr = (struct sctp_addiphdr *)last_asconf->subh.addip_hdr;
+		addip_hdr = last_asconf->subh.addip_hdr;
 		sent_serial = ntohl(addip_hdr->serial);
 	} else {
 		sent_serial = asoc->addip_serial - 1;