main/linux-lts: Enable CONFIG_CGROUP_PIDS for linux-lts ppc64le

To resolve an issue with failing to start k8s's kubelet:

F0627 15:23:40.684395   24145 kubelet.go:1383] Failed to start ContainerManager failed to initialize top level QOS containers: failed to update top level Burstable QOS cgroup : failed to set supported cgroup subsystems for cgroup [kubepods burstable]: failed to find subsystem mount for required subsystem: pids