staging: comedi: contec_pci_dio: cleanup contec_do_insn_bits

Create local variables for the mask and bits values passed in
the data pointer to make this function a bit clearer.

Return the state of the output bits (s->state) in data[1] since
this is what comedilib is expecting.

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>