Changes

bts: use proper ActType in f_TC_data_rtp_loopback()

For the sake of correctness, use c_RSL_IE_ActType_ASS (assignment)
when activating TCH/[FH] channels in TC_data_rtp_*.  This is the
kind of ActType that would normally be used by the BSC.

Change-Id: Ide773c3fcfdab881756d5fe5b6c314b0c0335043