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