zephyr/serial_recovery: fix serial device binding

zephyr changes the way in which it provide name of
serial device used by serial recover.
see: https://github.com/zephyrproject-rtos/zephyr/pull/18752



This path introduce build time configuration of device name
which is set to exact the same device which was set before.

Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>