osmo-bsc-{master,latest}/osmo-bsc.cfg: set AMR link adaptation params
The default AMR link adaptation parameters have been changed in
the recent osmo-bsc, so set the old expected default explicitly.
Change-Id: Ic1c46d54ef97278100bd52156ad5627418ef5c97
Related: osmo-bsc.git Ic5f8d55d250976d8d4c9cae2d89480fd52326717
Related: SYS#5917
