rspro_client_fsm: Make RSPRO transmit use FSM event

This way we can easily guarantee that RSPRO transmit will only happen
in the fully established state, and that violations of that rule will
generate error logs by means of osmo_fsm core logging code.

Change-Id: I3c403507fa11c068d7503107857fbd5676ce135f
diff --git a/src/rspro_client_fsm.h b/src/rspro_client_fsm.h
index c11e260..7a998dc 100644
--- a/src/rspro_client_fsm.h
+++ b/src/rspro_client_fsm.h
@@ -10,6 +10,7 @@
 	SRVC_E_TCP_DOWN,
 	SRVC_E_KA_TIMEOUT,
 	SRVC_E_CLIENT_CONN_RES,
+	SRVC_E_RSPRO_TX		/* transmit a RSPRO PDU to the peer */
 };
 
 struct rspro_server_conn;