USB: Disable USB2 LPM at shutdown

The QCA Rome USB Bluetooth controller has several issues once LPM gets
enabled:
- Fails to get enumerated in coldboot. [1]
- Drains more power (~ 0.2W) when the system is in S5. [2]
- Disappears after a warmboot. [2]

The issue happens because the device lingers at LPM L1 in S5, so device
can't get enumerated even after a reboot.

Disable LPM at shutdown to solve the issue.

[1] https://bugs.launchpad.net/bugs/1757218
[2] https://patchwork.kernel.org/patch/10607097/

Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Link: https://lore.kernel.org/r/20190805142412.23965-1-kai.heng.feng@canonical.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/port.c

@@ -285,6 +285,14 @@ static int usb_port_runtime_suspend(struct device *dev)
 }
 #endif
 
+static void usb_port_shutdown(struct device *dev)
+{
+	struct usb_port *port_dev = to_usb_port(dev);
+
+	if (port_dev->child)
+		usb_disable_usb2_hardware_lpm(port_dev->child);
+}
+
 static const struct dev_pm_ops usb_port_pm_ops = {
 #ifdef CONFIG_PM
 	.runtime_suspend =	usb_port_runtime_suspend,
@@ -301,6 +309,7 @@ struct device_type usb_port_device_type = {
 static struct device_driver usb_port_driver = {
 	.name = "usb",
 	.owner = THIS_MODULE,
+	.shutdown = usb_port_shutdown,
 };
 
 static int link_peers(struct usb_port *left, struct usb_port *right)