usb: core: notify disconnection when core detects disconnect

It is safe to call notify disconnect when the usb core
thinks the device is disconnected.

This commit also fixes one bug found at below situation:
we have not enabled usb wakeup, we do system suspend when
there is an usb device at the port, after suspend, we plug out
the usb device, then plug in device again. At that time,
the nofity disconnect was not called at current code, as
the controller doesn't know the usb device was disconnected
during the suspend, but USB core knows the port has changed
during that periods.

So to fix this problem, and let the usb core call notify disconnect.

Cc: 3.17+ <stable@vger.kernel.org>
Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>