usb: wusbcore: send keepalives to unauthenticated devices

This patch modifies the WUSB device disconnect timer code to send
keepalives to all connected devices even if they are not authenticated.
This fixes a problem where unauthenticated devices that lose their
connection before they are authenticated will stay in the device tree
forever.  More importantly, devices in this situation will never
relinquish their port on the root hub so eventually all root ports will
be taken up and no other devices can connect.

A comment in the existing code states that there are some devices that
may not respond to keepalives if they have not been authenticated.  That
comment is about 5 years old and I don't know of any WUSB devices that
act that way.  Either way, any buggy devices that may still be around
will continue to work as long as they can transition to the
authenticated state within the WUSB LOA timeout of 4s, which is not
unreasonable to expect.

Signed-off-by: Thomas Pugliese <thomas.pugliese@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>