ARM: dts: msm: Increase CPR DN threshold to 8

The change increases DN_THRESH to 8 to mitigate the voltage ripple
upto 50mV on VDD_APC on 8939 MTP & CDP platforms.

CRs-Fixed: 714468
Change-Id: I1776abe31ec144a6377ecbebf79ab7723cd8d384
Signed-off-by: Tirupathi Reddy <tirupath@codeaurora.org>