radeonsi: enable ARB_sparse_buffer

v2:
- fill in DRM version requirement
- disable on SI due to CP DMA faults

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
diff --git a/docs/features.txt b/docs/features.txt
index 1e145e1..6513c69 100644
--- a/docs/features.txt
+++ b/docs/features.txt
@@ -298,7 +298,7 @@
   GL_ARB_shader_group_vote                              DONE (nvc0, radeonsi)
   GL_ARB_shader_stencil_export                          DONE (i965/gen9+, radeonsi, softpipe, llvmpipe, swr)
   GL_ARB_shader_viewport_layer_array                    DONE (i965/gen6+)
-  GL_ARB_sparse_buffer                                  not started
+  GL_ARB_sparse_buffer                                  DONE (radeonsi/CIK+)
   GL_ARB_sparse_texture                                 not started
   GL_ARB_sparse_texture2                                not started
   GL_ARB_sparse_texture_clamp                           not started