mm: remove is_migrate_highatomic()

There are 3 potential reasons for is_migrate_*() helpers:

1. They represent higher-level attributes of migratetypes, like
   is_migrate_movable()

2. They are ifdef'd, like is_migrate_isolate().

3. For consistency with an is_migrate_*_page() helper, also like
   is_migrate_isolate().

It looks like is_migrate_highatomic() was for case 3, but that was
removed in commit e0932b6c1f ("mm: page_alloc: consolidate free page
accounting").

So remove the indirection and go back to a simple comparison.

Link: https://lkml.kernel.org/r/20250821-is-migrate-highatomic-v1-1-ddb6e5d7c566@google.com
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: SeongJae Park <sj@kernel.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/internal.h

@@ -1333,11 +1333,6 @@ extern const struct trace_print_flags pageflag_names[];
 extern const struct trace_print_flags vmaflag_names[];
 extern const struct trace_print_flags gfpflag_names[];
 
-static inline bool is_migrate_highatomic(enum migratetype migratetype)
-{
-	return migratetype == MIGRATE_HIGHATOMIC;
-}
-
 void setup_zone_pageset(struct zone *zone);
 
 struct migration_target_control {

mm/page_alloc.c

@@ -797,7 +797,7 @@ static inline void account_freepages(struct zone *zone, int nr_pages,
 
 	if (is_migrate_cma(migratetype))
 		__mod_zone_page_state(zone, NR_FREE_CMA_PAGES, nr_pages);
-	else if (is_migrate_highatomic(migratetype))
+	else if (migratetype == MIGRATE_HIGHATOMIC)
 		WRITE_ONCE(zone->nr_free_highatomic,
 			   zone->nr_free_highatomic + nr_pages);
 }