a_iface: Centralize/wrap BSSAP / N-DATA transmission

We don't want multiple callers to osmo_sccp_tx_data_msg() each having
to hex-dump a log message about the to-be-transmitted message, with
half of the caller sitest missing that printing.  Let's centralize
all calls of osmo_sccp_tx_data_msg() in a wrapper function which
takes care of the related OSMO_ASSERT() and the related printing.

Change-Id: I6159ea72cc8e0650eda6c49544acd65e9c15e817
4 files changed