blk-wbt: make enable_state more accurate

mainline inclusion
from mainline-v6.2-rc1
commit a9a236d2
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6Z1UG
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v6.3&id=a9a236d238a5e8ab2e74ca62c2c7ba5dd435af77



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Currently, if user disable wbt through sysfs, 'enable_state' will be
'WBT_STATE_ON_MANUAL', which will be confusing. Add a new state
'WBT_STATE_OFF_MANUAL' to cover that case.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221019121518.3865235-4-yukuai1@huaweicloud.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>