kvm: debugfs: aarch64 export cpu time related items to debugfs

euleros inclusion
category: feature
bugzilla: NA
CVE: NA

This patch export cpu time related items to vcpu_stat.
Contain:
	steal, st_max, utime, stime, gtime

The definitions of these items are:
steal: cpu time VCPU waits for PCPU while it is servicing another VCPU
st_max: max scheduling delay
utime: cpu time in userspace
stime: cpu time in sys
gtime: cpu time in guest

Through these items, user can get many cpu usage info of vcpu, such as:
CPU Usage of Guest =  gtime_delta / delta_cputime
CPU Usage of Hyp = (utime_delta - gtime_delta + stime_delta) / delta_cputime
CPU Usage of Steal = steal_delta / delta_cputime
Max Scheduling Delay = st_max

Signed-off-by: liangpeng <liangpeng10@huawei.com>
Signed-off-by: chenjiajun <chenjiajun8@huawei.com>
Reviewed-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>