anv: enable the GPL feature based on whether the extension is supported

Instead of checking if the very same bit we want to enable is already
enabled, which obviously doesn't work.

Fixes: fbc0e74bda ("anv: enable graphics pipeline libraries by default")

Acked-by: Nanley Chery <nanley.g.chery@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23039>

src/intel/vulkan/anv_device.c

@@ -590,7 +590,7 @@ get_features(const struct anv_physical_device *pdevice,
 
       /* VK_EXT_graphics_pipeline_library */
       .graphicsPipelineLibrary =
-         pdevice->vk.supported_features.graphicsPipelineLibrary,
+         pdevice->vk.supported_extensions.EXT_graphics_pipeline_library,
 
       /* VK_KHR_fragment_shading_rate */
       .pipelineFragmentShadingRate = true,