scsi: check the whole result for reading write protect flag

hulk inclusion
category: bugfix
bugzilla: NA
CVE: NA

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When the scsi device status is offline, mode sense command will return a
result with only DID_NO_CONNECT set. Then in sd_read_write_protect_flag(),
only status byte of the result is checked, we still consider the command
returned good, and read sdkp->write_prot from the buffer. And because of
bug [1], garbage data is copied to the buffer, the disk sometimes
be set readonly. When the scsi device is set running again, users cannot
write data to the disk.

Fix this by check the whole result returned by the driver.

[1] https://patchwork.kernel.org/project/linux-block/patch/20210318122621.330010-1-yanaijie@huawei.com/



Signed-off-by: Jason Yan <yanaijie@huawei.com>
Reviewed-by: Yufen Yu <yuyufen@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>