perf: replace cpu_up/down with device_online/offline

The cpu_up/down calls do not update userspace cpu
online information accurately. Use the device_on/offline
API to correct this.

Change-Id: I97ab55f4f917bd9cbb31dd89785eecdbe4d2f9ca
Signed-off-by: Neil Leeder <nleeder@codeaurora.org>