Remove more circular header dependencies (#37185)

Continuation of systemd/systemd#37112

Author: DaanDeMeyer

url-discovery.h

@@ -1,4 +1,6 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 #pragma once
 
+#include "efi.h"
+
 char16_t *disk_get_url(EFI_HANDLE *handle);