driconf: add workaround for Enter The Gungeon

driconf: add workaround for Enter The Gungeon

Quoting a comment on the bug report:

   I suspect the shader is incorrect.

   When a (conditional) discard is executed then control flow
   becomes non-uniform, meaning that subsequent implicit
   derivatives required for the texture operation are not
   computed correctly.

Using glsl_correct_derivatives_after_discard fixes it. Note
that for radeonsi this requires LLVM master to work properly.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/1386
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8005>