hulk inclusion
category: feature
feature: performance/latency
upstream: never
bugzilla: 2680,10641
CVE: NA

The pervious patch "kmod: run usermodehelpers only on cpus allowed for
kthreadd V2" allow to set usermodehelper thread's affinity.

add a interface to disable/enable usermodhelper_affinity.
Disabled by default.

[XQ: backport patch from euleros 2.x:
  - kmod.c => umh.c
]
Signed-off-by: NXie XiuQi <xiexiuqi@huawei.com>
Reviewed-by: NLi Bin <huawei.libin@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>