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>

drivers/lora/sx127x.c

@@ -658,6 +658,7 @@ static int sx127x_lora_init(const struct device *dev)
 static const struct lora_driver_api sx127x_lora_api = {
 	.config = sx12xx_lora_config,
 	.send = sx12xx_lora_send,
+	.send_async = sx12xx_lora_send_async,
 	.recv = sx12xx_lora_recv,
 	.test_cw = sx12xx_lora_test_cw,
 };