vc4: do not report alpha-test as supported

This triggers lowering in the state-tracker, which makes things a bit
simpler.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7251>

src/gallium/drivers/vc4/vc4_program.c

@@ -1803,11 +1803,6 @@ ntq_emit_intrinsic(struct vc4_compile *c, nir_intrinsic_instr *instr)
                                            0));
                 break;
 
-        case nir_intrinsic_load_alpha_ref_float:
-                ntq_store_dest(c, &instr->dest, 0,
-                               qir_uniform(c, QUNIFORM_ALPHA_REF, 0));
-                break;
-
         case nir_intrinsic_load_sample_mask_in:
                 ntq_store_dest(c, &instr->dest, 0,
                                qir_uniform(c, QUNIFORM_SAMPLE_MASK, 0));
@@ -2256,13 +2251,6 @@ vc4_shader_ntq(struct vc4_context *vc4, enum qstage stage,
         c->s = nir_shader_clone(c, key->shader_state->base.ir.nir);
 
         if (stage == QSTAGE_FRAG) {
-                if (c->fs_key->alpha_test_func != COMPARE_FUNC_ALWAYS) {
-                        NIR_PASS_V(c->s, nir_lower_alpha_test,
-                                   c->fs_key->alpha_test_func,
-                                   c->fs_key->sample_alpha_to_one &&
-                                   c->fs_key->msaa,
-                                   NULL);
-                }
                 NIR_PASS_V(c->s, vc4_nir_lower_blend, c);
         }
 

src/gallium/drivers/vc4/vc4_screen.c

@@ -199,6 +199,9 @@ vc4_screen_get_param(struct pipe_screen *pscreen, enum pipe_cap param)
         case PIPE_CAP_UMA:
                 return 1;
 
+        case PIPE_CAP_ALPHA_TEST:
+                return 0;
+
         default:
                 return u_pipe_screen_get_param_defaults(pscreen, param);
         }