Linux 5.7 Seeing Radeon FreeSync Fixes, Back-Ported Soft Recovery For Navi

While yesterday GFX10/Navi soft recovery support was sent in to DRM-Next for Linux 5.8, today that material was sent in as a "fix" for Linux 5.7 along with a number of other AMDGPU driver alterations.

The GFX10/Navi soft recovery is similar to what was already wired up for GFX9/Vega and allows for killing the waves for hung shaders as opposed to the existing GPU reset functionality already in place. This soft recovery support will help improve the experience ideally should any problems be encountered with shaders as opposed to needing a full GPU reset.

This pull request also has FreeSync fixes around vblank and page-flip event handling. This fixes several issues in the AMD display code around a potential race condition in DCN, an interrupt problem, etc.

Rounding out this pull for Linux 5.7 are also clock-gating fixes, an S4 fix for Navi, a DP MST fix, and other fixes.