dvfs tegra21: Decouple GPU capping and scaling cdevs

dvfs tegra21: Decouple GPU capping and scaling cdevs

Updated GPU thermal caps initialization so that caps are still applied
even if GPU thermal scaling cooling device is not present, or failed
initialization. In this case capping rates cannot be adjusted for
each scaling themperature range, and worst case caps are used.

Bug 1588362

Change-Id: I479922335baf123e6655d00866c827bed0e541ee
Signed-off-by: Alex Frid <afrid@nvidia.com>
Reviewed-on: http://git-master/r/727334
Reviewed-by: Bo Yan <byan@nvidia.com>