Transceiver: Fix idle ul burst indications being dropped
Transceiver: Fix idle ul burst indications being dropped

pullRadioVector() should return true on idle frames because those
indications may be handled by upper layers (TRXDv1). Clarify return code
in function documentation.

Change-Id: If592ed1c04cf7e995f656b313f60edd4d40d1bfd

osmocom/osmo-trx,osmocom/osmo-trx,osmocom/osmo-trx,osmocom/osmo-trx