net: lwm2m: add missing optional resource to firmware object
net: lwm2m: add missing optional resource to firmware object

Firmware Update Protocol Support resource initialization
has been left out in #41402.
Initialise the resource in object creation function.

Signed-off-by: Marin Jurjević <b0cd402275f93db923f965efd471b503030e79b6@hotmail.com>

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