staging: comedi: adv_pci1710: rename pci171x_d[io]_insn_bits

Rename these functions so they have namespace associated with the driver.

For aesthetics, move the functions so they are not located in the middle
of the analog input/output support functions.

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>