cpu/lpc2387: gpio: Don't discriminate between rising & falling pins
cpu/lpc2387: gpio: Don't discriminate between rising & falling pins

The `test_irq()` function does not discriminate between rising and
falling pins, so there is no need to handle them separately.

jasonatran/RIOT,basilfx/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,yogo1212/RIOT,OlegHahm/RIOT,yogo1212/RIOT,miri64/RIOT,miri64/RIOT,miri64/RIOT,yogo1212/RIOT,OTAkeys/RIOT,OlegHahm/RIOT,ant9000/RIOT,yogo1212/RIOT,basilfx/RIOT,OTAkeys/RIOT,miri64/RIOT,ant9000/RIOT,kaspar030/RIOT,kaspar030/RIOT,yogo1212/RIOT,jasonatran/RIOT,authmillenon/RIOT,basilfx/RIOT,OlegHahm/RIOT,authmillenon/RIOT,ant9000/RIOT,ant9000/RIOT,authmillenon/RIOT,jasonatran/RIOT,OTAkeys/RIOT,kYc0o/RIOT,kaspar030/RIOT,kYc0o/RIOT,jasonatran/RIOT,kYc0o/RIOT,OlegHahm/RIOT,kaspar030/RIOT,OTAkeys/RIOT,basilfx/RIOT,ant9000/RIOT,basilfx/RIOT,OlegHahm/RIOT,kYc0o/RIOT,authmillenon/RIOT,OTAkeys/RIOT,RIOT-OS/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,kaspar030/RIOT,authmillenon/RIOT,RIOT-OS/RIOT,yogo1212/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,miri64/RIOT