Add Dynamic Voltage and Frequency Scaling Driver Class

[Cheng-Li1]

Add the DVFS(Dynamic Voltage and Frequency Scaling) driver class and associated interfaces, and the implementation of the DVFS driver for the ZCU102 platform.

[midnightveil]

Same comment as previous: is there a design written up for this that we can look at?

[Cheng-Li1]

Same comment as previous: is there a design written up for this that we can look at?

Writing the doc now. Should be available soon.

[Cheng-Li1]

I have added a section about DVFS in the design doc.