net: gptp: Set stack size correctly for handler thread
net: gptp: Set stack size correctly for handler thread

The gptp stack size was not properly set, one must use
the K_THREAD_STACK_SIZEOF() macro to calculate stack size.

Signed-off-by: Jukka Rissanen <f9f077d1da4c7aa947f9864fa5a28c3588f6a45d@linux.intel.com>

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