net: lwm2m: clear lwm2m_obj_path obj in string_to_path
net: lwm2m: clear lwm2m_obj_path obj in string_to_path

Before ever call of string_to_path(), the lwm2m_obj_path object
was being cleared via memset.  Let's move the memset into
string_to_path() to remove the duplicate code.

Signed-off-by: Michael Scott <17b9e1c64588c7fa6419b4d29dc1f4426279ba01@opensourcefoundries.com>

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