staging: comedi: fl512: define the register map

Define the register map and remove the magic values and some unnecessary
comments.

For aesthetics, remove the 'iobase' local variable and use dev->iobase
directly.

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>