staging: ipack: remove irq field in struct ipack_device.

The field irq currently is identical to the slot number.  It does not seem to
have any real use.  The number is written to hardware in ipoctal but it seems
the value that is written does not matter.

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>