mm: fold and remove lru_cache_add_anon() and lru_cache_add_file()

They're the same function, and for the purpose of all callers they are
equivalent to lru_cache_add().

[akpm@linux-foundation.org: fix it for local_lock changes]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Rik van Riel <riel@surriel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Link: http://lkml.kernel.org/r/20200520232525.798933-5-hannes@cmpxchg.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memory.c

@@ -3139,7 +3139,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 				if (err)
 					goto out_page;
 
-				lru_cache_add_anon(page);
+				lru_cache_add(page);
 				swap_readpage(page, true);
 			}
 		} else {