radeonsi: Add GFX9+ modifier support.
This adds modifier support to radeonsi.
It has been tested on
- VEGA10, RAVEN, NAVI14
- weston, sway, X with xf86-video-amdgpu (i.e. legacy path still works)
and includes some basic testing of the layout code.
Kernel support: https://patchwork.freedesktop.org/series/80262/ (https://github.com/BNieuwenhuizen/linux/tree/modifiers)
Edited by Bas Nieuwenhuizen