osmotrx: configuration: Add section to document multi-arfcn feature
osmotrx: configuration: Add section to document multi-arfcn feature

Change-Id: Id04c7f7c36d8a8be8145ef8009ece26ef1a7cdff

osmocom/osmo-trx,osmocom/osmo-trx,osmocom/osmo-trx,ttsou/osmo-trx,osmocom/osmo-trx,ttsou/osmo-trx,ttsou/osmo-trx,ttsou/osmo-trx