staging: comedi: s626: cleanup s626_dio_insn_config()

Add some local variables to make this function a bit cleaner.

The comedi core expects this function to return the number of
data parameters used. Change the return from '1' to insn->n to
make this more aparent.

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>