soc/tegra: dvfs: Add function to predict millivolts at max thermal floor

soc/tegra: dvfs: Add function to predict millivolts at max thermal floor

Add helper function tegra_dvfs_predict_mv_at_hz_max_tfloor() to predict
the millivolts for a rail at max thermal floor. This is needed for CPU
EDP.

Bug 1811732

Change-Id: I2d66a3d14776ffd46da962b671e70b0c90fc28b5
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Reviewed-on: http://git-master/r/1281372
Reviewed-by: Peter De Schrijver <pdeschrijver@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Jon Mayo <jmayo@nvidia.com>