vty: add a command to show GPRS related info
vty: add a command to show GPRS related info

Here is a sample output:

  OsmoBTS# show bts 0 gprs
  BTS 0, RAC 0, NSEI 101, BVCI 2
    Cell NM state: Oper 'Enabled', Admin 'Unlocked', Avail 'OK'
    NSE NM state: Oper 'Enabled', Admin 'Unlocked', Avail 'OK'
    NSVC0 (NSVCI 101) NM state: Oper 'Enabled', Admin 'Unlocked', Avail 'OK'
      Address: r=127.0.0.1:23010<->l=0.0.0.0:55385
    NSVC1 (NSVCI 0) NM state: Oper 'Disabled', Admin 'Locked', Avail 'Off line'

This command is useful for debugging NS connection problems.

Change-Id: I149eea0b1c109020406eb67c9082c335a77aab06

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