bts: Move conf_for_bsc_prepare from bts_osmo to bts

nanobts inherits directly from bts.Bts, so we need to move
conf_for_bsc_prepare there to make nanobts work again.

Fixes: 530681fd86c4a4dab18e4575c9cdf339623ffa49
Change-Id: I4305eefb4056ed7614118532e271efe780f4a87f
2 files changed