drivers: gpio_nrfx: update to use new GPIO API

Update driver code and board files to use new GPIO configuration flags
such as GPIO_ACTIVE_LOW. Also add implementation of new port_* driver
API as well as gpio_pin_interrupt_configure function.

Tested on nrf52840_pca10056 board.

Signed-off-by: Piotr Mienkowski <piotr.mienkowski@gmail.com>
Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>
22 files changed