gprs: Set bssgph field in bssgp_msgb_alloc()

Currently the bssgph field is not set when using the bssgp_tx_*
functions. This hinders unit testing of generated messages.

This patch initializes the bssgph field directly after allocation a
new bssgp msgb in bssgp_msgb_alloc() so that it is set by default.

Sponsored-by: On-Waves ehf
1 file changed