s390/mm,pageattr: fix walk_pte_level() early exit

In case of splitting to 4k mapping the early exit in walk_pte_level()
must only be taken iff flags is equal to SET_MEMORY_4K.
Currently the early exit is taken if the flag is set, and also others
might be set. This may lead to the situation that a mapping is split
but other changes are not done, like e.g. setting pages to R/W.

There is currently no such caller, but there might be in the future.

Fixes: b3e1a00c ("s390/mm: implement set_memory_4k()")
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/mm/pageattr.c

@@ -86,7 +86,7 @@ static int walk_pte_level(pmd_t *pmdp, unsigned long addr, unsigned long end,
 {
 	pte_t *ptep, new;
 
-	if ((flags & SET_MEMORY_4K) == SET_MEMORY_4K)
+	if (flags == SET_MEMORY_4K)
 		return 0;
 	ptep = pte_offset_kernel(pmdp, addr);
 	do {