powerpc/windfarm: const'ify and add "priv" field to controls & sensors

const'ify the sensor ops and name and add a void* for use by
the control and sensor drivers to point back to their private
data, avoiding the need to create a wrapper data structure
per sensor or control instance.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
1 file changed