gsm_pchan2chan_nr: move warning to pragma message and track issue
gsm_pchan2chan_nr: move warning to pragma message and track issue

Take the chance to move the default option to the end as it's the
usually expected syntax.

Change-Id: I21298fcd0d1c1aafdd3dc1e8c8dae37b271b1d3d

osmocom/osmo-bts,osmocom/osmo-bts,osmocom/osmo-bts