net: lwm2m: remove unused members from lwm2m_output_context
net: lwm2m: remove unused members from lwm2m_output_context

Now that formatters use their own private data to hold state,
let's remove the old member variables from lwm2m_output_context
which are now unused.

Signed-off-by: Michael Scott <a17fed27eaa842282862ff7c1b9c8395a26ac320@foundries.io>

explora26/zephyr,nashif/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,punitvara/zephyr,explora26/zephyr,explora26/zephyr,kraj/zephyr,punitvara/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,nashif/zephyr,Vudentz/zephyr,ldts/zephyr,nashif/zephyr,ldts/zephyr,finikorg/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,ldts/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,kraj/zephyr,nashif/zephyr,ldts/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,galak/zephyr,galak/zephyr,punitvara/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,kraj/zephyr,finikorg/zephyr,punitvara/zephyr,explora26/zephyr