AMDGPU Fixes For Linux 5.5 Include AMDKFD For PowerPC, Fix For Old ATI R100/R200 GPUs

Following last week's big batch of DRM graphics driver updates for the Linux 5.5 merge window, AMD and the community engaging in Linux 5.5 testing have now sent in their first round of fixes for this next version of the Linux kernel.

While focused on bug fixing, this pull request does bring some notable changes to the AMDGPU Linux 5.5 code:

- While not a "fix" in the traditional sense, this pull does include the AMDKFD patch to work on IBM POWER CPUs. The AMD GPU compute driver can work fine on PowerPC in its current state, so this patch is just exposing it when building the Linux kernel for the architecture. Patches to the Radeon Open eCosystem (ROCm) stack in user-space for making those bits friendly with POWER are still pending. Kudos to Raptor Computing Systems for working on the AMDKFD+ROCm POWER bits so users running the likes of the POWER9 Blackbird and Talos II can enjoy this open-source GPU compute stack.

- A fix to the register checker for old ATI R100/R200 driver. This is a low impact change but fun to see R100/R200 hardware seeing any driver activity as we approach 2020. The fix was just a code mistake noticed by developer Alex Deucher in passing.

- Navi 14 Display Core (DC) fixes.

- The AMDKFD page table reservation code has been improved so that in an extreme case of multiple graphics cards and lots of system memory no longer leads to around 1GB of memory being dedicated to page table reservations per GPU but now only around 32MB.

There are also other minor fixes as outlined via the pull request.