drivers: lora: Add user_data to lora_recv_async

The LoRa driver does not allow to pass void* user_data to callback in
lora_recv_async function. This leads to complex way of using the API. This
commit fixes the issue and adds the field to the function and to the
callback.

Signed-off-by: Aleksander Dejewski <aleksander.dejewski@gmail.com>