mm/page_io.c: remove useless out label in __swap_writepage()

mm/page_io.c: remove useless out label in __swap_writepage()

The out label is only used in one place and return ret directly without
something like resource cleanup or lock release and so on.  So we should
remove this jump label and do some cleanup.

Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Link: https://lkml.kernel.org/r/20200927124032.22521-1-linmiaohe@huawei.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>