staging: comedi: addi_apci_3120: use correct iobase to write AMCC registers

The AMCC registers are accessed using the base address devpriv->i_IobaseAmcc
not devpriv->i_IobaseAddon. Fix a couple writes in apci3120_interrupt_dma()
that are using the wrong base address.

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>