md: fix unexpected changes of return value in rdev_set_badblocks

hulk inclusion
category: bugfix
bugzilla: 188569, https://gitee.com/openeuler/kernel/issues/I6XBZQ


CVE: NA

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If we set any badblocks fail, we will remove this rdev(set it to Faulty
or set recovery_disabled). Previous patch "md/raid10: fix io hung in
md_wait_for_blocked_rdev()" check badblocks->changed instead of return
value in rdev_set_badblocks(), but return value of this func also changed
accordingly, which is not what we expected.

Keep the return value consistent with before.

Signed-off-by: Li Nan <linan122@huawei.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Hou Tao <houtao1@huawei.com>