staging: comedi: drivers: remove inappropriate SDF_* flags from subdevices

The SDF_GROUND, SDF_COMMON, SDF_DIFF, and SDF_OTHER flags are only useful
with the analog input and output subdevices.

Remove these flags from the other subdevice types in the comedi drivers.

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>