md/raid10: remove WANR_ON_ONCE in raid10_end_write_request

hulk inclusion
category: bugfix
bugzilla: 188605, https://gitee.com/openeuler/kernel/issues/I6GOYF


CVE: NA

--------------------------------

It might read mirror.redev first and then mirror->replacement because of
memory reordering in raid10_end_write_request(), WARN_ON occurs if we
remove disk at the same time.

  T1 remove			T2 io end
  raid10_remove_disk		raid10_end_write_request
   p->rdev = NULL
				 read rdev -> NULL
   smp_mb
   p->replacement = NULL
				 read replacement -> NULL

It is meaningless to compare rdev with mirror->rdev after we get it from
r10_bio in raid10_end_write_request(). Remove this WANR_ON_ONCE.

Fixes: 2ecf5e6ecbfd ("md/raid10: fix uaf if replacement replaces rdev")
Signed-off-by: Li Nan <linan122@huawei.com>
Reviewed-by: Hou Tao <houtao1@huawei.com>