rxrpc: Cache the security index in the rxrpc_call struct

Cache the security index in the rxrpc_call struct so that we can get at it
even when the call has been disconnected and the connection pointer
cleared.

Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/net/rxrpc/sendmsg.c b/net/rxrpc/sendmsg.c
index 803078b..2439aff 100644
--- a/net/rxrpc/sendmsg.c
+++ b/net/rxrpc/sendmsg.c
@@ -322,7 +322,7 @@
 			sp->hdr.serial	= atomic_inc_return(&conn->serial);
 			sp->hdr.type	= RXRPC_PACKET_TYPE_DATA;
 			sp->hdr.userStatus = 0;
-			sp->hdr.securityIndex = conn->security_ix;
+			sp->hdr.securityIndex = call->security_ix;
 			sp->hdr._rsvd	= 0;
 			sp->hdr.serviceId = call->service_id;