anv: Fix -Wswitch in anv_layout_to_aux_usage()

anv_layout_to_aux_usage() lacked a case for
VK_IMAGE_LAYOUT_SHARED_PRESENT_KHR. Add an unreachable case, because we
don't support the extension.

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

src/intel/vulkan/anv_image.c

@@ -520,6 +520,9 @@ anv_layout_to_aux_usage(const struct gen_device_info * const devinfo,
    case VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL:
       assert(!color_aspect);
       return ISL_AUX_USAGE_HIZ;
+
+   case VK_IMAGE_LAYOUT_SHARED_PRESENT_KHR:
+      unreachable("VK_KHR_shared_presentable_image is unsupported");
    }
 
    /* If the layout isn't recognized in the exhaustive switch above, the