aerofc: forbid gpio changes

We export an "empty" table, but there's no protection when doing
ioctl().

src/drivers/px4fmu/fmu.cpp

@@ -2560,7 +2560,11 @@ PX4FMU::gpio_ioctl(struct file *filp, int cmd, unsigned long arg)
 	case GPIO_SET_OUTPUT_HIGH:
 	case GPIO_SET_INPUT:
 	case GPIO_SET_ALT_1:
+#ifdef CONFIG_ARCH_BOARD_AEROFC_V1
+		ret = -EINVAL;
+#else
 		gpio_set_function(arg, cmd);
+#endif
 		break;
 
 	case GPIO_SET_ALT_2:
@@ -2571,11 +2575,19 @@ PX4FMU::gpio_ioctl(struct file *filp, int cmd, unsigned long arg)
 
 	case GPIO_SET:
 	case GPIO_CLEAR:
+#ifdef CONFIG_ARCH_BOARD_AEROFC_V1
+		ret = -EINVAL;
+#else
 		gpio_write(arg, cmd);
+#endif
 		break;
 
 	case GPIO_GET:
+#ifdef CONFIG_ARCH_BOARD_AEROFC_V1
+		ret = -EINVAL;
+#else
 		*(uint32_t *)arg = gpio_read();
+#endif
 		break;
 
 	default: