zephyr: disable qspi-nor on nrf52840

Sine https://github.com/zephyrproject-rtos/zephyr/pull/47629

 was
merged the qspi nod driver is enabled by default. This cause unwanted
flash footprint rise for configurations which are not using the qspi.

This patch disables it back.

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