x86: return -EINVAL in __change_page_attr(), instead of 0

careful: might change driver behavior - but this is the right
return value.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/mm/pageattr_64.c

@@ -135,7 +135,7 @@ __change_page_attr(unsigned long address, struct page *page, pgprot_t prot)
 repeat:
 	kpte = lookup_address(address, &level);
 	if (!kpte)
-		return 0;
+		return -EINVAL;
 
 	kpte_page = virt_to_page(kpte);
 	BUG_ON(PageLRU(kpte_page));