USB: fix autosuspend bug in usb-serial

This patch (as1437) fixes a bug in the usb-serial autosuspend
handling.  Since the usb-serial core now has autosuspend support, it
must set the .supports_autosuspend member in every serial driver it
registers.  Otherwise the usb_autopm_get_interface() call won't work.

This fixes Bugzilla #23012.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: stable@kernel.org
Reported-by: Kevin Smith <thirdwiggin@gmail.com>
Reported-and-tested-by: Simon Gerber <gesimu@gmail.com>
Reported-and-tested-by: Matteo Croce <matteo@openwrt.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/usb-serial.c

@@ -51,6 +51,7 @@ static struct usb_driver usb_serial_driver = {
 	.suspend =	usb_serial_suspend,
 	.resume =	usb_serial_resume,
 	.no_dynamic_id = 	1,
+	.supports_autosuspend =	1,
 };
 
 /* There is no MODULE_DEVICE_TABLE for usbserial.c.  Instead
@@ -1343,6 +1344,8 @@ int usb_serial_register(struct usb_serial_driver *driver)
 		return -ENODEV;
 
 	fixup_generic(driver);
+	if (driver->usb_driver)
+		driver->usb_driver->supports_autosuspend = 1;
 
 	if (!driver->description)
 		driver->description = driver->driver.name;