vty: fix doc str for 'reset sgsn state'

Document all keywords of the 'reset sgsn state' command: set the same doc
string for all three.

Also fixes the build after libosmocore
I1f18e0e41da4772d092d71261b9e489dc1598923, which resulted in HIDDEN commands
coming up in the VTY reference dumping. Note that libosmocore
I92c3c66ff69c186234276c64478d6342e061d25e will again remove this breakage by
omitting hidden commands.

Change-Id: I8b6e8615e409266910f2f76a10ced9ab33e4de91
1 file changed