Staging: ipack/devices/ipoctal: put ipoctal_channel into tty->driver_data.

Each tty's driver_data is now pointing to the channel it is talking to.  struct
ipoctal_channel contains all the information the callbacks require to do their
work.

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