x86/p2m: clean up altp2m

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -618,9 +618,11 @@ void p2m_teardown(struct p2m_domain *p2m
 
 void p2m_final_teardown(struct domain *d)
 {
-    /* We must teardown unconditionally because
+    /*
+     * We must teardown both of them unconditionally because
      * we initialise them unconditionally.
      */
+    p2m_teardown_altp2m(d);
     p2m_teardown_nestedp2m(d);
 
     /* Iterate over all p2m tables per domain */