memcg: remove mem_cgroup_cache_charge_swapin()

mem_cgroup_cache_charge_swapin() isn't used any more, so remove no-op
definition of it in header file.
Signed-off-by: NDaisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

include/linux/swap.h

@@ -423,12 +423,6 @@ static inline swp_entry_t get_swap_page(void)
 #define has_swap_token(x) 0
 #define disable_swap_token() do { } while(0)
 
-static inline int mem_cgroup_cache_charge_swapin(struct page *page,
-			struct mm_struct *mm, gfp_t mask, bool locked)
-{
-	return 0;
-}
-
 static inline void
 mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent)
 {