ioport: Add an ioctl to get the port state

ioport: Add an ioctl to get the port state

Example:
for (int i = 'A'; i <= 'F'; i++) {	avr_ioport_state_t state;
	if (avr_ioctl(AVR_IOCTL_IOPORT_GETSTATE(i), &state) == 0)
		printf("PORT%c %02x DDR %02x PIN %02x\n",
			state.name, state.port, state.ddr, state.pin);
}

Signed-off-by: Michel Pollet <buserror@gmail.com>