mm/page_alloc: use deferred_pages_enabled() wherever applicable

Instead of directly accessing static deferred_pages, replace such
instances with the helper deferred_pages_enabled().  No functional change
is intended.

Link: https://lkml.kernel.org/r/20230105082506.241529-1-anshuman.khandual@arm.comSigned-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/page_alloc.c

@@ -4288,7 +4288,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
 			 * Watermark failed for this zone, but see if we can
 			 * grow this zone if it contains deferred pages.
 			 */
-			if (static_branch_unlikely(&deferred_pages)) {
+			if (deferred_pages_enabled()) {
 				if (_deferred_grow_zone(zone, order))
 					goto try_this_zone;
 			}
@@ -4337,7 +4337,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
 		} else {
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
 			/* Try again if zone has deferred pages */
-			if (static_branch_unlikely(&deferred_pages)) {
+			if (deferred_pages_enabled()) {
 				if (_deferred_grow_zone(zone, order))
 					goto try_this_zone;
 			}