sh: asm/tlb.h needs linux/swap.h

Commit 1e56a56410bb64bce62d44563e35a143fc2d515f introduced the mmu_gather
rework for sh, but missed a linux/swap.h include:

CC arch/sh/mm/tlb-urb.o
In file included from arch/sh/mm/tlb-urb.c:14:0:
arch/sh/include/asm/tlb.h: In function '__tlb_remove_page':
arch/sh/include/asm/tlb.h:92:2: error: implicit declaration of function 'free_page_and_swap_cache'

Signed-off-by: Nobuhiro Iwamatsu <[e-mail]>
CC: Peter Zijlstra <[e-mail]>
Signed-off-by: Paul Mundt <[e-mail]>

arch/sh/include/asm/tlb.h

···
 #include <linux/pagemap.h>
 
 #ifdef CONFIG_MMU
+#include <linux/swap.h>
 #include <asm/pgalloc.h>
 #include <asm/tlbflush.h>
 #include <asm/mmu_context.h>