usb: gadget: f_accessory: Fix for UsbAccessory clean unbind.

Reapplying fix by Darren Whobrey (Change 69674)

Fixes issues: 20545, 59667 and 61390.
With prior version of f_accessory.c, UsbAccessories would not
unbind cleanly when application is closed or i/o stopped
while the usb cable is still connected. The accessory gadget
driver would be left in an invalid state which was not reset
on subsequent binding or opening. A reboot was necessary to clear.

In some phones this issues causes the phone to reboot upon
unplugging the USB cable.

Main problem was that acc_disconnect was being called on I/O error
which reset disconnected and online.

Minor fix required to properly track setting and unsetting of
disconnected and online flags. Also added urb Q wakeup's on unbind
to help unblock waiting threads.

Tested on Nexus 7 grouper. Expected behaviour now observed:
closing accessory causes blocked i/o to interrupt with IOException.
Accessory can be restarted following closing of file handle
and re-opening.

This is a generic fix that applies to all devices.

Change-Id: I4e08b326730dd3a2820c863124cee10f7cb5501e
Signed-off-by: Darren Whobrey <d.whobrey@mildai.org>
Signed-off-by: Anson Jacob <ansonjacob.aj@gmail.com>