mm/damon/vaddr: constify static mm_walk_ops

The only usage of these structs is to pass their addresses to
walk_page_range(), which takes a pointer to const mm_walk_ops as
argument.  Make them const to allow the compiler to put them in
read-only memory.

Link: https://lkml.kernel.org/r/20211014075042.17174-2-rikard.falkeborn@gmail.comSigned-off-by: NRikard Falkeborn <rikard.falkeborn@gmail.com>
Reviewed-by: NSeongJae Park <sj@kernel.org>
Reviewed-by: NAnshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/damon/vaddr.c

@@ -394,7 +394,7 @@ static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned long addr,
 	return 0;
 }
 
-static struct mm_walk_ops damon_mkold_ops = {
+static const struct mm_walk_ops damon_mkold_ops = {
 	.pmd_entry = damon_mkold_pmd_entry,
 };
 
@@ -490,7 +490,7 @@ static int damon_young_pmd_entry(pmd_t *pmd, unsigned long addr,
 	return 0;
 }
 
-static struct mm_walk_ops damon_young_ops = {
+static const struct mm_walk_ops damon_young_ops = {
 	.pmd_entry = damon_young_pmd_entry,
 };