Staging: ipack/devices/ipoctal: avoid kernel oops when uninstalling

When uninstalling a device, there is a loop of calls that produces, at the end,
two calls to __ipoctal_remove() function with the same ipack_device argument.

The first time works fine, but the second will fail in tty_unregister_driver()

To avoid this situation, the call to __ipoctal_remove() it is done only from the
ipack bus driver and not from the ipack device driver.

Signed-off-by: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>