s390/mm: ignore change bit for vmemmap

Add hint to the page tables that we don't care about the change bit
in storage keys that belong to vmemmap pages.

Signed-off-by: Heiko Carstens <[e-mail]>
Signed-off-by: Martin Schwidefsky <[e-mail]>

arch/s390/mm/vmem.c

···
 				if (!new_page)
 					goto out;
 				pmd_val(*pm_dir) = __pa(new_page) |
-					_SEGMENT_ENTRY | _SEGMENT_ENTRY_LARGE;
+					_SEGMENT_ENTRY | _SEGMENT_ENTRY_LARGE |
+					_SEGMENT_ENTRY_CO;
 				address = (address + PMD_SIZE) & PMD_MASK;
 				continue;
 			}