usbcore: set lpm_capable field for LPM capable root hubs

commit 9df89d85b407690afa46ddfbccc80bec6869971d upstream.

This patch sets the lpm_capable field for root hubs with LPM capabilities.

Signed-off-by: Xenia Ragiadakou <burzalodowa@gmail.com>
Reported-by: Martin MOKREJS <mmokrejs@gmail.com>
Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 896532d..c8b9fa0 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -135,7 +135,7 @@
 	return usb_get_intfdata(hdev->actconfig->interface[0]);
 }
 
-static int usb_device_supports_lpm(struct usb_device *udev)
+int usb_device_supports_lpm(struct usb_device *udev)
 {
 	/* USB 2.1 (and greater) devices indicate LPM support through
 	 * their USB 2.0 Extended Capabilities BOS descriptor.
@@ -156,6 +156,11 @@
 				"Power management will be impacted.\n");
 		return 0;
 	}
+
+	/* udev is root hub */
+	if (!udev->parent)
+		return 1;
+
 	if (udev->parent->lpm_capable)
 		return 1;