portability: Warn at void* arithmetics which is a GNU C extension
portability: Warn at void* arithmetics which is a GNU C extension

Ensure future commits do not re-introduce use of this GNU C extension.

Signed-off-by: Mark Ruvald Pedersen <3c05dc905675c0722f67ee578faf639727313efa@oticon.com>

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