[Sightlineapplications] GPU stability patches

Hi Kim,

I'm attaching four patches for you to test. They are to be applied on top of the single-GPU-freq patch, but after additional testing I'll push them to the main repo too.

First patch is pretty obvious and targets overall device stability (marking yet another memory region as reserved).

Second and third patches ensure that the GPU GX domain is not toggled too quickly (which can cause it to lock down), while the fourth patch follows the vendor kernel and ensures that GFX3D is clocked during GPU GX domain operations.