staging: comedi: adl_pci9111: cleanup pci9111_do_insn_bits()

Remove the unnecessary comments.

Cleanup the function to follow the comedi standard for digital
outputs. The 'mask' does not need to be checked, the comedi core
will make sure that it is valid based on the subdevice data.
The outputs only need to be updated if the 'mask' indicates
something is changing, otherwise we just need to return the
current "state" of the outputs.

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