staging: fsl-mc-bus: fix build warning

error could be unitialized when it is used as a return value in
fsl_mc_device_add().  So fix up the warning by properly setting it.

Cc: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/fsl-mc/bus/fsl-mc-bus.c

@@ -570,6 +570,7 @@ int fsl_mc_device_add(struct fsl_mc_obj_desc *obj_desc,
 	mc_dev->dev.release = fsl_mc_device_release;
 	mc_dev->dev.type = fsl_mc_get_device_type(obj_desc->type);
 	if (!mc_dev->dev.type) {
+		error = -ENODEV;
 		dev_err(parent_dev, "unknown device type %s\n", obj_desc->type);
 		goto error_cleanup_dev;
 	}