Call usb_gadget_vbus_connect() and ...disconnect() from a
workqueue rather than from an irq handler, allowing msleep()
calls in vbus_session.  Update kerneldoc to match.

[ dbrownell@users.sourceforge.net: more kerneldoc updates ]
Signed-off-by: NRobert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>