drivers: gpio: gpio_mcux_lpc: Use arbitrary amount of IRQ

Zephyr implementation is limited to 4 IRQ per GPIO bank when up to 8 is
theoritically possible.

It is now possible to use until 8 IRQ per GPIO bank. This can be
achieved with minimal effort in a device tree overlay:

&gpio0 {
	interrupts = <4 2>,<5 2>,<6 2>,<7 2>,<32 2>,<33 2>;
};

&gpio1 {
	interrupts = <34 2>,<35 2>;
};

Signed-off-by: Guy Morand <guy.morand@bytesatwork.ch>