x86/mm: address Misra C:2012 rule 16.2

... ("A switch label shall only be used when the most closely-enclosing
compound statement is the body of a `switch' statement"). Use a form of
fall-through instead. No difference in generated code, except for some
line number changes.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>

xen/arch/x86/mm.c

@@ -2663,15 +2663,17 @@ static int validate_page(struct page_info *page, unsigned long type,
                  get_gpfn_from_mfn(mfn_x(page_to_mfn(page))),
                  type, page->count_info, page->u.inuse.type_info);
         if ( page != current->arch.old_guest_table )
-            page->u.inuse.type_info = 0;
-        else
         {
-            ASSERT((page->u.inuse.type_info &
-                    (PGT_count_mask | PGT_validated)) == 1);
-    case -ERESTART:
-            get_page_light(page);
-            page->u.inuse.type_info |= PGT_partial;
+            page->u.inuse.type_info = 0;
+            break;
         }
+
+        ASSERT((page->u.inuse.type_info &
+                (PGT_count_mask | PGT_validated)) == 1);
+        fallthrough;
+    case -ERESTART:
+        get_page_light(page);
+        page->u.inuse.type_info |= PGT_partial;
         break;
     }