hasvk: Enable PixelShaderKillsPixel when omask is used

From the Haswell PRM Vol. 2b, 3DSTATE_WM::Pixel Shader Kill Pixel:
    "This bit is required to be ENABLED in the following situations:
     - The API pixel shader program contains "killpix" or "discard"
       instructions, or other code in the pixel shader kernel that can
       cause the final pixel mask to differ from the pixel mask received
       on dispatch.
     - A sampler with chroma key enabled with kill pixel mode is used by
       the pixel shader.
     - Any render target has Alpha Test Enable or AlphaToCoverage Enable
       enabled.
     - The pixel shader kernel generates and outputs oMask."

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19876>

src/intel/vulkan_hasvk/genX_pipeline.c

@@ -1597,7 +1597,8 @@ emit_3dstate_wm(struct anv_graphics_pipeline *pipeline,
        */
       wm.PixelShaderKillsPixel         = rp->depth_self_dependency ||
                                          rp->stencil_self_dependency ||
-                                         wm_prog_data->uses_kill;
+                                         wm_prog_data->uses_kill ||
+                                         wm_prog_data->uses_omask;
 
       pipeline->force_fragment_thread_dispatch =
          wm.PixelShaderComputedDepthMode != PSCDEPTH_OFF ||