agch: Add VTY queue management configuration
agch: Add VTY queue management configuration

This patch adds the following VTY commands to tune AGCH queue
handling:

  agch-queue-management default
  agch-queue-management threshold THRES low LOW high HIGH

Examples:
  agch-queue-management default
    Resets queue management to default parameters.
  agch-queue-management threshold 0 low 25 high 75
    Start dropping at 25%, drop all messages above 75% queue length
    (relative to max queue length corresponding to T3126). Between
    low and high, drop with a probability interpolated linearly
    between 0 (low) and 1 (high).
  agch-queue-management threshold 50 low 0 high 0
    Start dropping at 50% and continue until all IMM.ASS.REJ have
    been removed from the front (output) of the queue

Sponsored-by: On-Waves ehf

geosphere/osmo-bts,telenoobie/osmo-bts,geosphere/osmo-bts,osmocom/osmo-bts,geosphere/osmo-bts,telenoobie/osmo-bts,osmocom/osmo-bts,osmocom/osmo-bts,geosphere/osmo-bts,telenoobie/osmo-bts,telenoobie/osmo-bts