anv: Enable SPV_KHR_8bit_storage and VK_KHR_8bit_storage

Enables SPV_KHR_8bit_storage and VK_KHR_8bit_storage on gen 8+
using the VK_KHR_get_physical_device_properties2 functionality
to expose if the extension is supported or not.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/intel/vulkan/anv_pipeline.c

@@ -153,6 +153,7 @@ anv_shader_compile_to_nir(struct anv_pipeline *pipeline,
          .subgroup_shuffle = true,
          .subgroup_vote = true,
          .stencil_export = device->instance->physicalDevice.info.gen >= 9,
+         .storage_8bit = device->instance->physicalDevice.info.gen >= 8,
       },
    };