gpio: pcie-idio-24: Use -ENOTSUPP consistently

The GPIO library expects the drivers to return -ENOTSUPP in some cases
and not using analogue POSIX code. Make the driver to follow this.

Signed-off-by: Andy Shevchenko <[e-mail]>
Acked-by: William Breathitt Gray <[e-mail]>
Reviewed-by: Linus Walleij <[e-mail]>
Signed-off-by: Bartosz Golaszewski <[e-mail]>

drivers/gpio/gpio-pcie-idio-24.c

···
 	case IDIO_24_CONTROL_REG:
 		/* We can only set direction for TTL/CMOS lines */
 		if (offset < 48)
-			return -EOPNOTSUPP;
+			return -ENOTSUPP;
 
 		*reg = IDIO_24_CONTROL_REG;
 		*mask = CONTROL_REG_OUT_MODE;