PCI: hv: Avoid use of hv_pci_dev->pci_slot after freeing it

The slot must be removed before the pci_dev is removed, otherwise a panic
can happen due to use-after-free.

Fixes: 15becc2b56 ("PCI: hv: Add hv_pci_remove_slots() when we unload the driver")
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: stable@vger.kernel.org

drivers/pci/controller/pci-hyperv.c

@@ -2701,8 +2701,8 @@ static int hv_pci_remove(struct hv_device *hdev)
 		/* Remove the bus from PCI's point of view. */
 		pci_lock_rescan_remove();
 		pci_stop_root_bus(hbus->pci_bus);
-		pci_remove_root_bus(hbus->pci_bus);
 		hv_pci_remove_slots(hbus);
+		pci_remove_root_bus(hbus->pci_bus);
 		pci_unlock_rescan_remove();
 		hbus->state = hv_pcibus_removed;
 	}