Transceiver: Drop unused rssi_valid struct field

That field is actually never used. Furthermore, if pullRadioVector()
returns false, then the caller should consider the 'trx_ul_burst_ind'
structure as uninitialized. Moreover, RSSI is mandatory - we cannot send
burst indications without it.

Related: OS#4006
Change-Id: Ia109298aebe8ba4750a39338ba7962555903cd82
2 files changed