drivers: lora: Add CheckRfFrequency callback to SX1276 driver
drivers: lora: Add CheckRfFrequency callback to SX1276 driver

CheckRfFrequency was not assigned correctly to the Radio. This lead
to the system hang when the loramac library tries to call a relevant
Radio method when processing a join-accept message

Signed-off-by: Kuba Sanak <1a73af9e7ae00182733b2292511b814be66f065f@kuba.fyi>
Signed-off-by: Manivannan Sadhasivam <c29222e98de6437a383e8d946a9b202298e0aa3a@kernel.org>

zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,nashif/zephyr,Vudentz/zephyr,Vudentz/zephyr,galak/zephyr,Vudentz/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,Vudentz/zephyr,Vudentz/zephyr,nashif/zephyr,finikorg/zephyr,nashif/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,galak/zephyr,galak/zephyr,galak/zephyr