lora: compile drivers based on devicetree

Similar to the changes made in #48048, compile in the appropriate lora
modem driver when `CONFIG_LORA=y`. The `LORA_SX12XX` symbol has no
use now so remove. LoRa and LoRaWAN subsystems are still marked as
unstable so no additional deprecation cycle is needed.

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