Add thermal zone details and enable the PWM fan as cooling device.

Note that this also changes the cooling levels for the PWM fan, which
should have no effect, though, because the fan wasn't previously
connected to anything and by default would be turned off at probe time.
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>