staging: fsl-mc: fix asymmetry in destroy of mc_io

An mc_io represents a mapped MC portal.  Previously, an mc_io was
created for the root dprc in fsl_mc_bus_probe() and for child dprcs
in dprc_probe().  But the free of that data structure happened in the
general bus remove callback.  This asymmetry resulted in some bugs due
to unwanted destroys of mc_io object in some scenarios (e.g. vfio).

Fix this bug by making things symmetric-- mc_io created in
fsl_mc_bus_probe() is freed in fsl_mc_bus_remove().  The mc_io created
in dprc_probe() is freed in dprc_remove().
Signed-off-by: Bharat Bhushan <Bharat.Bhushan@nxp.com>
[Stuart: added check for root dprc and reworded commit message]
Signed-off-by: Stuart Yoder <stuart.yoder@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

@@ -801,6 +801,11 @@ static int dprc_remove(struct fsl_mc_device *mc_dev)
 		dev_set_msi_domain(&mc_dev->dev, NULL);
 	}
 
+	if (!fsl_mc_is_root_dprc(&mc_dev->dev)) {
+		fsl_destroy_mc_io(mc_dev->mc_io);
+		mc_dev->mc_io = NULL;
+	}
+
 	dev_info(&mc_dev->dev, "DPRC device unbound from driver");
 	return 0;
 }

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

@@ -579,10 +579,6 @@ void fsl_mc_device_remove(struct fsl_mc_device *mc_dev)
 
 	if (strcmp(mc_dev->obj_desc.type, "dprc") == 0) {
 		mc_bus = to_fsl_mc_bus(mc_dev);
-		if (mc_dev->mc_io) {
-			fsl_destroy_mc_io(mc_dev->mc_io);
-			mc_dev->mc_io = NULL;
-		}
 
 		if (fsl_mc_is_root_dprc(&mc_dev->dev)) {
 			if (atomic_read(&root_dprc_count) > 0)
@@ -810,6 +806,10 @@ static int fsl_mc_bus_remove(struct platform_device *pdev)
 		return -EINVAL;
 
 	fsl_mc_device_remove(mc->root_mc_bus_dev);
+
+	fsl_destroy_mc_io(mc->root_mc_bus_dev->mc_io);
+	mc->root_mc_bus_dev->mc_io = NULL;
+
 	dev_info(&pdev->dev, "Root MC bus device removed");
 	return 0;
 }