gprs: Fix and check BVCI in BSSGP STATUS messages

Currently the BVCI is not set in all invocations to bssgp_tx_status()
when the cause is UNKNOWN_BVCI.

This patch adds the argument where it is missing.

It also adds a check for compliance (GSM 08.18, 10.4.14.1) to
bssgp_tx_status() to emit errors when the following requirement is
not fulfilled: The BVCI must be included if (and only if) the cause
is either "BVCI blocked" or "BVCI unknown".

Sponsored-by: On-Waves ehf
2 files changed