i2c: i2c-mux-gpio: use deferred probing

If the i2c-parent bus driver is not loaded, returning
-ENODEV will force people to unload and then reload the
module again to get it working.
Signed-off-by: Ionut Nicu <ioan.nicu.ext@nsn.com>
Acked-by: Peter Korsgaard <peter.korsgaard@barco.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/muxes/i2c-mux-gpio.c

@@ -79,7 +79,7 @@ static int i2c_mux_gpio_probe_dt(struct gpiomux *mux,
 	adapter = of_find_i2c_adapter_by_node(adapter_np);
 	if (!adapter) {
 		dev_err(&pdev->dev, "Cannot find parent bus\n");
-		return -ENODEV;
+		return -EPROBE_DEFER;
 	}
 	mux->data.parent = i2c_adapter_id(adapter);
 	put_device(&adapter->dev);
@@ -181,7 +181,7 @@ static int i2c_mux_gpio_probe(struct platform_device *pdev)
 	if (!parent) {
 		dev_err(&pdev->dev, "Parent adapter (%d) not found\n",
 			mux->data.parent);
-		return -ENODEV;
+		return -EPROBE_DEFER;
 	}
 
 	mux->parent = parent;