workqueue: Change arguement of pwq_dec_nr_in_flight()

mainline inclusion
from mainline-v5.15-rc1
commit c4560c2c
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7LRJF

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c4560c2c88a4c809800ba8e76faabaf80bf6ee89



---------------------------

Make pwq_dec_nr_in_flight() use work_data rather just work_color.

Prepare for later patch to get WORK_STRUCT_INACTIVE bit from work_data
in pwq_dec_nr_in_flight().

No functional change intended.

Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Zeng Heng <zengheng4@huawei.com>