mesa: only emit _NEW_MULTISAMPLE when sample mask changes

We usually check that given parameters are different before
updating the state.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>

src/mesa/main/multisample.c

@@ -119,6 +119,9 @@ _mesa_SampleMaski(GLuint index, GLbitfield mask)
       return;
    }
 
+   if (ctx->Multisample.SampleMaskValue == mask)
+      return;
+
    FLUSH_VERTICES(ctx, _NEW_MULTISAMPLE);
    ctx->Multisample.SampleMaskValue = mask;
 }