USB: usb-serial: replace shutdown with disconnect, release

USB: usb-serial: replace shutdown with disconnect, release

This is commit f9c99bb8b3a1ec81af68d484a551307326c2e933 back-ported to
2.6.27.39.

This patch (as1254-2) splits up the shutdown method of usb_serial_driver
into a disconnect and a release method.

The problem is that the usb-serial core was calling shutdown during
disconnect handling, but drivers didn't expect it to be called until
after all the open file references had been closed.  The result was an
oops when the close method tried to use memory that had been
deallocated by shutdown.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Rory Filer <rfiler@SierraWireless.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>