powerpc/windfarm: Fix XServe G5 fan control Makefile issue
powerpc/windfarm: Fix XServe G5 fan control Makefile issue

We are missing building windfarm_max6690_sensor.o when building
CONFIG_WINDFARM_RM31. Usually all the windfarm drivers are built
and thus this isn't a problem but some more "tailored" setups
(Gentoo ?) building only that driver are not working because
the require sensor module is missing.

Reported-by: Stanislav Ponomarev <48b0bc6a5eaaee02399fc6756b2979fd8291cf62@gmail.com>
Signed-off-by: Benjamin Herrenschmidt <a7089bb6e7e92505d88aaff006cbdd60cc9120b6@kernel.crashing.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs