ipa: Add E1INP_SIGN_OSMO to use IPAC_PROTO_OSMO via e1_input

In order to make use of the IPAC_PROTO_OSMO stream_id of the IPA
multiplex via the e1_input abstraction layer, we need to define
E1INP_SIGN_OSMO and treat it like other signalling (OML/RSL).

This is required for the upcoming code that uses IPAC_PROTO_OSMO
to remotely insert routing table entries into the OML router (e.g. from
osmo-bts).
3 files changed