gprs_gmm: Fix missing Security Command for 3G when attaching

Introduce a new FSM step in GMM Attach to send the
Security Command to the RNC after completing the
Authentication.

Fixes: f7198d7dbb84 ("gprs_gmm: introduce a GMM Attach Request FSM")
Change-Id: I1e12b0a32e58c6f78dba7b548f7d7016567229db
diff --git a/include/osmocom/sgsn/gprs_gmm_attach.h b/include/osmocom/sgsn/gprs_gmm_attach.h
index 22fbd6f..0aa2123 100644
--- a/include/osmocom/sgsn/gprs_gmm_attach.h
+++ b/include/osmocom/sgsn/gprs_gmm_attach.h
@@ -11,6 +11,7 @@
 	ST_RETRIEVE_AUTH,
 	ST_AUTH,
 	ST_ASK_VLR,
+	ST_IU_SECURITY_CMD,
 	ST_ACCEPT,
 	ST_REJECT
 };
@@ -20,6 +21,7 @@
 	E_IDEN_RESP_RECV,
 	E_AUTH_RESP_RECV_SUCCESS,
 	E_AUTH_RESP_RECV_RESYNC,
+	E_IU_SECURITY_CMD_COMPLETE,
 	E_ATTACH_ACCEPTED,
 	E_ATTACH_ACCEPT_SENT,
 	E_ATTACH_COMPLETE_RECV,