arm64/mpam: add num_monitors in info dir

hulk inclusion
category: feature
feature: ARM MPAM support
bugzilla: 48265
CVE: NA

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root@(none)$ pwd
/sys/fs/resctrl/info
root@(none)$ grep . */*
L3/num_partids:32
L3_MON/num_monitors:8
L3_MON/num_pmgs:4
MB/num_partids:16
MB_MON/num_monitors:16
MB_MON/num_pmgs:4

Signed-off-by: Xie XiuQi <xiexiuqi@huawei.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
Reviewed-by: Cheng Jian <cj.chengjian@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>