drivers: sx126x_standalone: use the correct dev_data for dio1 callback

The current code uses dev->data for finding back the instance data
structure in various places, but for the dio1 irq callback, dev refers
to the GPIO device node (not the LORA radio one), so dev->data returns a
pointer to the GPIO data rather than a "struct sx126x_data".

Fix that by using CONTAINER_OF to find back the correct structure from
the callback pointer.

The bug was introduced in:

  74efaa92 drivers: sx126x: refactor few functions for stm32wl support

Signed-off-by: Fabio Baltieri <fabio.baltieri@gmail.com>