arm64/mpam: decrease dom_num when domain goes offline

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I61CPK


CVE: NA

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mpam_resctrl_setup_domain() increase dom_num when domain goes online. As
a result, mpam_resctrl_cpu_offline() should decrease dom_num when domain
goes offline.

Signed-off-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>
Reviewed-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>