mm: memory-failure: make action_result() return int

Check mf_result in action_result(), only return 0 when MF_RECOVERED,
or return -EBUSY, which will simplify code a bit.

[wangkefeng.wang@huawei.com: v2]
  Link: https://lkml.kernel.org/r/20221024035138.99119-1-wangkefeng.wang@huawei.com
Link: https://lkml.kernel.org/r/20221021084611.53765-3-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>