net/ieee802154: Make sure L2 drop any ACK frames
net/ieee802154: Make sure L2 drop any ACK frames

Though ACK frames are not meant to reach L2 (drivers must ensure this
never happens), let's "re-enforce" the L2 by dropping them.

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

Vudentz/zephyr,Vudentz/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,finikorg/zephyr,nashif/zephyr,nashif/zephyr,Vudentz/zephyr,finikorg/zephyr,nashif/zephyr,galak/zephyr,Vudentz/zephyr,nashif/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr