freedreno/a3xx: add support for S8 and Z32F_S8

Enables ARB_depth_buffer_float. There is no sampling support for
interleaved Z32F_S8, so we store the two textures separately, one as
Z32F, the other as S8. As a result, we need a lot of additional logic
for restores and transfers.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>

docs/relnotes/10.6.0.html

@@ -46,6 +46,7 @@ Note: some of the new features are only available with certain drivers.
 <ul>
 <li>GL_AMD_pinned_memory on r600, radeonsi</li>
 <li>GL_ARB_clip_control on i965</li>
+<li>GL_ARB_depth_buffer_float on freedreno</li>
 <li>GL_ARB_depth_clamp on freedreno</li>
 <li>GL_ARB_draw_indirect, GL_ARB_multi_draw_indirect on r600</li>
 <li>GL_ARB_draw_instanced on freedreno</li>