net: lwm2m: report resource type / content type at registration
net: lwm2m: report resource type / content type at registration

Per LwM2M specification 5.3.1 Register, report "ct=11543" when JSON is
supported. Also, report the resource type as rt="oma.lwm2m" when "ct="
presents.

Signed-off-by: Robert Chou <563fc56b80720efb29939356d471536b8c17d514@acer.com>

runchip/zephyr-cc3220,aceofall/zephyr-iotos,zephyrproject-rtos/zephyr,ldts/zephyr,zephyriot/zephyr,nashif/zephyr,punitvara/zephyr,zephyrproject-rtos/zephyr,aceofall/zephyr-iotos,galak/zephyr,kraj/zephyr,nashif/zephyr,nashif/zephyr,runchip/zephyr-cc3220,Vudentz/zephyr,galak/zephyr,Vudentz/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,aceofall/zephyr-iotos,aceofall/zephyr-iotos,mbolivar/zephyr,fbsder/zephyr,zephyriot/zephyr,Vudentz/zephyr,Vudentz/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,fbsder/zephyr,punitvara/zephyr,runchip/zephyr-cc3220,mbolivar/zephyr,ldts/zephyr,kraj/zephyr,kraj/zephyr,aceofall/zephyr-iotos,galak/zephyr,fbsder/zephyr,mbolivar/zephyr,zephyriot/zephyr,GiulianoFranchetto/zephyr,punitvara/zephyr,galak/zephyr,mbolivar/zephyr,runchip/zephyr-cc3220,explora26/zephyr,punitvara/zephyr,mbolivar/zephyr,Vudentz/zephyr,fbsder/zephyr,explora26/zephyr,finikorg/zephyr,zephyriot/zephyr,fbsder/zephyr,finikorg/zephyr,ldts/zephyr,explora26/zephyr,ldts/zephyr,kraj/zephyr,zephyriot/zephyr,zephyrproject-rtos/zephyr,punitvara/zephyr,explora26/zephyr,finikorg/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,nashif/zephyr,kraj/zephyr,runchip/zephyr-cc3220