ARM: dts: msm: update perf latency parameters for msm8939

Latency and overhead numbers are reduced for perf image.
Reduced latencies will result in power benefit by allowing
LPM logic to pick up a low power mode more aggressively.

Change-Id: Ibb911ac0df6322a78fab9d7b0518840ef64276dd
Signed-off-by: Anil Kumar Mamidala <amami@codeaurora.org>
Signed-off-by: Maulik Shah <mkshah@codeaurora.org>