Revert "move ASS-COMPL MGCP handling out of a_iface_bssap.c"

Two reasons:

- the caller of msc_mgcp_ass_complete() from Iu, iucs_rx_rab_assign(), failed
  to be adjusted, breaking IuCS, as an --enable-iu --enable-werror build shows.
  Unfortunately our gerrit verification doesn't --enable-werror for osmo-msc.

- the condition of requiring ST_MDCX_RAN is faulty, breaking GSM CS.

This reverts commit 212c0c9bdaf1166e3bcbab85f3ab31dc17162f5b.

Change-Id: I8348675c2f7c8856ea1682d05ee54160d4cfeb96
5 files changed