lora: `lora_send` blocks until completion

Change the behaviour of `lora_send` to block until the transmission
completes. The current asynchronous behaviour is exposed through the
new function `lora_send_async`. This naming convention brings LoRa in
line with other asynchronous subsystems.

Signed-off-by: Jordan Yates <jordan.yates@data61.csiro.au>
5 files changed