powerpc/windfarm: Updates to lm75 and max6690 sensors

powerpc/windfarm: Updates to lm75 and max6690 sensors

This allows those modules to load on PowerMac7,2 PowerMac7,3
and RackMac3,1 and add the sensor name conversion for those
machines.

This will be used by the corresponding new windfarm modules
for those machines.

Note that since therm_pm72 is linked first, it will still
take priority on those i2c devices if built-in. If using modules
it will depend which is loaded first, but you should avoid building
therm_pm72 if you are using the new windfarm drivers

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