block: fix kabi broken in struct hd_struct

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I57S8D


CVE: NA

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Use reserved fields to fix kabi broken for field 'stat_time'. However,
for the field 'bd_stat_lock', spinlock_t can be up to 64 bytes, thus
reserved fields is not enough. And struct 'hd_struct' is internal of
other sutrct, thus declare a wrapper is infeasible. In order to fix
kabi broken for 'bd_stat_lock', use 'dev->mutex' instead.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>