anv: Implement VK_KHX_external_semaphore_capabilities

This just stubs things out.  Real external semaphore support will come
with VK_KHX_external_semaphore_fd.

Reviewed-by: Chad Versace <chadversary@chromium.org>

src/intel/vulkan/anv_device.c

@@ -331,6 +331,10 @@ static const VkExtensionProperties global_extensions[] = {
       .extensionName = VK_KHX_EXTERNAL_MEMORY_CAPABILITIES_EXTENSION_NAME,
       .specVersion = 1,
    },
+   {
+      .extensionName = VK_KHX_EXTERNAL_SEMAPHORE_CAPABILITIES_EXTENSION_NAME,
+      .specVersion = 1,
+   },
 };
 
 static const VkExtensionProperties device_extensions[] = {