staging: comedi: addi_apci_1564: tidy up apci1564_reset()

The reset function for this driver is a bit of a mess; clean it up to
ensure that it is functioning properly.

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