Instead using static kconfig CONFIG_PSI_CGROUP_V1, we introduce a boot
parameter psi_v1 to enable psi cgroup v1 support. Default it is
disabled, which means when passing psi=1 boot parameter, we only support
cgroup v2.
This is to keep consistent with other cgroup v1 features such as cgroup
writeback v1 (cgwb_v1).
Signed-off-by: NJoseph Qi <joseph.qi@linux.alibaba.com>
Acked-by: NXunlei Pang <xlpang@linux.alibaba.com>