net/pkt: Add dummy getter/setters for IPv4/IPv6 attributes
net/pkt: Add dummy getter/setters for IPv4/IPv6 attributes

All as static inline functions to let the compiler check the types
etc... And use ARG_UNUSED() always where relevant.

Signed-off-by: Tomasz Bursztyka <ba81a3a719836727e6857ae83462b9f52ec41006@linux.intel.com>

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