mm/memory_failure: constify static mm_walk_ops

The only usage of hwp_walk_ops is to pass its address to walk_page_range()
which takes a pointer to const mm_walk_ops as argument.  Make it const to
allow the compiler to put it in read-only memory.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Rikard Falkeborn <[email protected]>
Acked-by: Naoya Horiguchi <[email protected]>
Reviewed-by: Anshuman Khandual <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Stephen Rothwell <[email protected]>

mm/memory-failure.c

@@ -674,7 +674,7 @@ static int hwpoison_hugetlb_range(pte_t *ptep, unsigned long hmask,
 #define hwpoison_hugetlb_range	NULL
 #endif
 
-static struct mm_walk_ops hwp_walk_ops = {
+static const struct mm_walk_ops hwp_walk_ops = {
 	.pmd_entry = hwpoison_pte_range,
 	.hugetlb_entry = hwpoison_hugetlb_range,
 };