Transceiver.cpp: use a define for the MAX_PACKET_LENGTH
Transceiver.cpp: use a define for the MAX_PACKET_LENGTH

No need to keep this value on stack.

Change-Id: If9ffb03b9e7b642f45732ba5938977bca271f1c7

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