anv: Advertise shaderIntegerFunctions2
We advertised the extension string but never the feature bit. Doh!
Fixes: c57338b9 "anv: Enable SPV_INTEL_shader_integer_functions2..."
The big question I have here is, how did we not notice? Are there no tests for this? Looks like there are some in crucible!59 (merged) but they never got landed. We should probably land them.