drm/vmwgfx: support 64 UAVs

If the host supports SVGA3D_DEVCAP_GL43, we can handle 64 instead of
just 8 UAVs.
Based on a patch from Roland Scheidegger <sroland@vmware.com>.

Signed-off-by: Roland Scheidegger <sroland@vmware.com>
Signed-off-by: Zack Rusin <zackr@vmware.com>
Reviewed-by: Martin Krastev <krastevm@vmware.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211206172620.3139754-9-zack@kde.org