vty: fix documentation for 'swap-channels (disable|enable)'
vty: fix documentation for 'swap-channels (disable|enable)'

Change-Id: Idca1a2beab07ef4df9ae5c55658cab80f7cc7565

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