net: lwm2m: Fix device obj missing error code ri
net: lwm2m: Fix device obj missing error code ri

From the OMA LwM2M Object and Resource Registry: "When the single Device
Object Instance is initiated, there is only one error code Resource
Instance whose value is equal to 0 that means no error."

This fix creates that initial error code resource instance, and makes
sure that it doesn't get deleted by the Reset Error Code resource.

Signed-off-by: Tjerand Bjornsen <56f0c9d71c470a543b35b98344562b5a95ff78b5@nordicsemi.no>

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