raid5: fix missing io accounting in raid5_align_endio()

Io will only be accounted as done from raid5_align_endio() if the io
succeeded, and io inflight counter will be leaked if such io failed.

Fix this problem by switching to use md_account_bio() for io accounting.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Xiao Ni <xni@redhat.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20230621165110.1498313-4-yukuai1@huaweicloud.com