Bluetooth: Controller: Add parameter to ISOALs sdu_write

For vendor datapaths that do not use a netbuffer to write SDUs
into, the callee of sdu_write currently has to keep track itself
of how much data has been written to the current SDU; This is wasteful
since ISOAL already keeps track of that. Add an sdu_written parameter
to the callback to inform the callee how much has been written to the
current SDU already so the callee can write using the correct offset

Signed-off-by: Troels Nilsson <trnn@demant.com>

tests/bsim/bluetooth/ll/bis/src/main.c

@@ -124,10 +124,11 @@ static isoal_status_t test_sink_sdu_emit(const struct isoal_sink             *si
 }
 
 static isoal_status_t test_sink_sdu_write(void *dbuf,
+					  const size_t sdu_written,
 					  const uint8_t *pdu_payload,
 					  const size_t consume_len)
 {
-	memcpy(dbuf, pdu_payload, consume_len);
+	memcpy((uint8_t *)dbuf + sdu_written, pdu_payload, consume_len);
 
 	return ISOAL_STATUS_OK;
 }