mm/swap.c: remove duplicated include

Remove duplicated include linux/memremap.h

Link: http://lkml.kernel.org/r/20180917131308.16420-1-yuehaibing@huawei.com


Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>