drivers: ieee802154: uart: Do not send FCS bytes to peer
drivers: ieee802154: uart: Do not send FCS bytes to peer

No need to send FCS bytes as the monitor_15_4 is configured to not
expect them. If we change the monitor_15_4 to use them, then we would
need to put correct values into these two FCS bytes.
So cleanest solution is not to send FCS bytes at all.

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

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