cgroup: Use 64bit id from kernfs

Use 64 bit id allocated by kernfs instead of using its own idr since
it seems not used for saving any information no more.  So let's get
rid of the cgroup_idr from cgroup_root.

The index of netprio_map is also changed to u64.

Cc: netprio cgroup people
Signed-off-by: Tejun Heo <tj@kernel.org>
[namhyung: split cgroup changes and fix netprio_map access]
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
4 files changed