drivers: nrfx_uarte: uarte_pm_suspend, please return -EAGAIN instead of kill the device with ASSERT

[Achim Kraus]

uart_nrfx_uarte.c, uarte_pm_suspend checks some preconditions with __ASSERT_NO_MSG. 

In my experience that causes unintended and not required crashes.

If the precondition is not full-filled, returning -EAGAIN would be a better choice.

See https://github.com/zephyrproject-rtos/zephyr/issues/105506 also.

[Achim Kraus]

Just to mention:

AI proposed some work-around.

In my opinion, it's just pretty bad to fail with an ASSERT instead of returning an error code.

[Elfving]

Hi,

Thanks for bringing this to our attention. I'll get back to you on this once I hear more from the relevant team on this.

Regards,

Elfving