library: L1CTL: merge L1ctl{Ul,Dl}Message into L1ctlMessage

Currently we have two variants of the L1CTL PDU:

* L1ctlUlMessage: L23 -> L1 requests (*_REQ),
* L1ctlDlMessage: L1 -> L23 responses (*_IND, *_CONF).

The L1CTL_PT port is defined in a way that one can:

* Tx L1ctl{Ul,Dl}Message PDUs,
* Rx L1ctlDlMessage PDUs.

This means that the testsuite can act as the L23 talking to the L1
(e.g. trxcon or virtphy), but not vice-versa.  Adding an additional
Rx `UD_send_data -> L1ctlUlMessage` mapping is not an option,
because such a mapping would be ambiguous and would cause errors.

By merging the two L1CTL PDU variants into the one, we can achieve
the testsuite acting as the L1.  This will be useful for testing
the L23 applications in osmocom-bb.git, like the modem app.

Take a chance to reorder fields to match the order in L1ctlMsgType.

Change-Id: I1313068c5f02b65d3dbb05a1341a9d7286225f0c
Related: OS#5500
5 files changed