staging: comedi: addi_apci_1564: fix timer iobase for all PLD revisions

The APCI-1564 has different I/O mapping depending on if the PLD revision
is Rev 1.0 or Rev 2.x.

Add a member, 'timer', to the private data for the base address of the
12-bit timer. Fix the register defines so they will work for all PLD
revisions and initialize the devpriv->timer appropriately.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>