mm/kasan/common.c: fix compile error

I hit the following compile error in arch/x86/

   mm/kasan/common.c: In function kasan_populate_vmalloc:
   mm/kasan/common.c:797:2: error: implicit declaration of function flush_cache_vmap; did you mean flush_rcu_work? [-Werror=implicit-function-declaration]
     flush_cache_vmap(shadow_start, shadow_end);
     ^~~~~~~~~~~~~~~~
     flush_rcu_work
   cc1: some warnings being treated as errors

Link: http://lkml.kernel.org/r/[email protected]
Fixes: 3c5c3cf ("kasan: support backing vmalloc space with real shadow memory")
Signed-off-by: zhong jiang <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Reviewed-by: Daniel Axtens <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/kasan/common.c

@@ -36,6 +36,7 @@
 #include <linux/bug.h>
 #include <linux/uaccess.h>
 
+#include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
 
 #include "kasan.h"