acpuclock: Overclocking added

Change-Id: I55ae9c09cdc9f8be906ffe5bd6843c5783fec368
acpuclock: OC stability fixes

Change-Id: I6252b195da4d60a6e146e94e036c3d32e84d3ea4
Signed-off-by: Randolf Kastenmaier <randolf.kastenmaier@gmail.com>