api: gpio: do not support INT flags in gpio_pin_configure

To keep compatibility between the old GPIO API implementation and a new
one introduced in the Zephyr 2.2.0 release the gpio_pin_configure()
function was accepting interrupt flags. In the new API implementation
interrupt flags are only accepted by gpio_pin_interrupt_configure()
function.

This temporary support for INT flags in gpio_pin_configure should have
been removed in the Zephyr 2.4.0 release.

Signed-off-by: Piotr Mienkowski <piotr.mienkowski@gmail.com>