scsi_lib: disable fair tag sharing by default if total tags is less than 128

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8RGGC


CVE: NA

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If total number of driver tags is little, disable the block layer fair tag
sharing algorithm because it significantly reduces performance, e.g.
UFS devices.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>