staging: pi433: fix error return code in pi433_probe()

Fix to return negative error code -ENOMEM from cdev alloc failed error
handling case instead of 0, as done elsewhere in this function.

Signed-off-by: Wei Yongjun <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/pi433/pi433_if.c

···
 	device->cdev = cdev_alloc();
 	if (!device->cdev) {
 		dev_dbg(device->dev, "allocation of cdev failed");
+		retval = -ENOMEM;
 		goto cdev_failed;
 	}
 	device->cdev->owner = THIS_MODULE;