net: lwm2m: use ARRAY_SIZE to calculate # of options
net: lwm2m: use ARRAY_SIZE to calculate # of options

Don't use hard-coded value of 4 for passing the # of options to
coap_find_options() in handle_request().  This can easily get
out of sync.

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

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