drivers: thermal: enable fan regulater when needed

drivers: thermal: enable fan regulater when needed

Only enable vdd-fan regulator before fan start spin for power saving
Disable vdd-fan regulator when next fan pwm is 0.

bug 200069439

Change-Id: If5e0c35472478e6197bb37ef2af52b540d855fc9
Signed-off-by: Terry Wang <terwang@nvidia.com>
(cherry picked from commit bc6092007fc42d7201f4520e0f0ae2d555dfe1a4)
Reviewed-on: http://git-master/r/714766
Reviewed-on: http://git-master/r/779289
Reviewed-by: Aaron Huang <aaronh@nvidia.com>
Reviewed-by: Laxman Dewangan <ldewangan@nvidia.com>