radv: add a workaround for DXVK hangs by setting amdgpu-skip-threshold

radv: add a workaround for DXVK hangs by setting amdgpu-skip-threshold

Workaround for bug in llvm that causes the GPU to hang in presence
of nested loops because there is an exec mask issue. The proper
solution is to fix LLVM but this might require a bunch of work.

This fixes a bunch of GPU hangs that happen with DXVK.

Vega10:
Totals from affected shaders:
SGPRS: 110456 -> 110456 (0.00 %)
VGPRS: 122800 -> 122800 (0.00 %)
Spilled SGPRs: 7478 -> 7478 (0.00 %)
Spilled VGPRs: 36 -> 36 (0.00 %)
Code Size: 9901104 -> 9922928 (0.22 %) bytes
Max Waves: 7143 -> 7143 (0.00 %)

Code size slightly increases because it inserts more branch
instructions but that's expected. I don't see any real performance
changes.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105613
Cc: mesa-stable@lists.freedesktop.org
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>