radv: correctly disable WGP_MODE for NGG GS on GFX10.3
Previously, we would set WGP_MODE on GFX10+ and then only on GFX10. Because we used bitwise or, the result was WGP_MODE being set on GFX10+.
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Previously, we would set WGP_MODE on GFX10+ and then only on GFX10. Because we used bitwise or, the result was WGP_MODE being set on GFX10+.