st/mesa: don't pass compare mode for stencil-sampled textures

Fixes dEQP-GLES31.functional.stencil_texturing.misc.compare_mode_effect

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Cc: mesa-stable@lists.freedesktop.org
(cherry picked from commit 3970257cef5e0c7b5b31c023450f1ea55b784e88)
diff --git a/src/mesa/state_tracker/st_atom_sampler.c b/src/mesa/state_tracker/st_atom_sampler.c
index daf98c3..661e0f2 100644
--- a/src/mesa/state_tracker/st_atom_sampler.c
+++ b/src/mesa/state_tracker/st_atom_sampler.c
@@ -226,7 +226,7 @@
 
    /* If sampling a depth texture and using shadow comparison */
    if ((texBaseFormat == GL_DEPTH_COMPONENT ||
-        texBaseFormat == GL_DEPTH_STENCIL) &&
+        (texBaseFormat == GL_DEPTH_STENCIL && !texobj->StencilSampling)) &&
        msamp->CompareMode == GL_COMPARE_R_TO_TEXTURE) {
       sampler->compare_mode = PIPE_TEX_COMPARE_R_TO_TEXTURE;
       sampler->compare_func = st_compare_func_to_pipe(msamp->CompareFunc);