drivers: nrf: avoid UARTE pm infinite loop
drivers: nrf: avoid UARTE pm infinite loop

calling UARTE power management with DEVICE_PM_SUSPEND_STATE
then DEVICE_PM_OFF_STATE causes a deadlock in while loop.
It waits for an event witch never comes

Signed-off-by: Ismael Fillonneau <442d9750715ea95535a4e2a8f6ddf109988eab86@stimio.fr>

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