Revert "assignment_fsm: Properly support assigning signalling mode TCH/x"

This commit breaks voice channel assignment. It results in the
Assignment Complete sent to the MSC for a voice lchan lacking
AoIP Transport Layer Address, Speech Version and Speech Codec.
Hence the MSC cannot complete the Assignment for a voice call.
Let's revisit this patch, test thoroughly and re-merge later.

This reverts commit 4d3a21269b25e7164a94fa8ce3ad67ff80904aee.

Reason for revert: <INSERT REASONING HERE>

Change-Id: I72aaa03539919e7e85b5b75b133326cec5e68bc9
8 files changed