usb: dwc3: imx8mp: fix error return code in dwc3_imx8mp_probe()

Fix to return a negative error code from the error handling case instead
of 0, as done elsewhere in this function.

Fixes: 6dd2565989 ("usb: dwc3: add imx8mp dwc3 glue layer driver")
Reported-by: Hulk Robot <hulkci@huawei.com>
Acked-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20210508015310.1627-1-thunder.leizhen@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/dwc3/dwc3-imx8mp.c

@@ -167,6 +167,7 @@ static int dwc3_imx8mp_probe(struct platform_device *pdev)
 
 	dwc3_np = of_get_compatible_child(node, "snps,dwc3");
 	if (!dwc3_np) {
+		err = -ENODEV;
 		dev_err(dev, "failed to find dwc3 core child\n");
 		goto disable_rpm;
 	}