drivers: can: mcux: Persuade the driver to send in chronological order
drivers: can: mcux: Persuade the driver to send in chronological order

The mcux CAN controller uses frame ID and position to calculate the
priority, but the driver expects chronological ordering.
This PR mimics this behavior by only using the last free message box.

Signed-off-by: Alexander Wachter <ce6e77dabd455f5e273537afd862be63bdedff84@student.tugraz.at>

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