Add new properties to configure the DFLL PWM regulator support.

Cc: devicetree@vger.kernel.org
Signed-off-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Signed-off-by: Joseph Lo <josephl@nvidia.com>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>