usb: xhci-pci: Add DM_FLAG_OS_PREPARE flag

The PCIe bus the controller is connected to might need to be removed
prior the handover. Make sure xhci-pci is also removed so as to avoid
unexpected timeouts or hangs.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Signed-off-by: Matthias Brugger <mbrugger@suse.com>
diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c
index 6c5024d..aaa243f 100644
--- a/drivers/usb/host/xhci-pci.c
+++ b/drivers/usb/host/xhci-pci.c
@@ -70,7 +70,7 @@
 	.ops	= &xhci_usb_ops,
 	.plat_auto	= sizeof(struct usb_plat),
 	.priv_auto	= sizeof(struct xhci_ctrl),
-	.flags	= DM_FLAG_ALLOC_PRIV_DMA,
+	.flags	= DM_FLAG_OS_PREPARE | DM_FLAG_ALLOC_PRIV_DMA,
 };
 
 static struct pci_device_id xhci_pci_supported[] = {