ARM: dts: msm: Remove VDD_MSS control from PIL on MDM9640

On MDM9640, the Q6 is powered by VDD_CX instead of VDD_MSS.
Therefore, remove the control of VDD_MSS from PIL.

Change-Id: I62fc6f8ed57095c95569f2be9198f8693e1437f9
Signed-off-by: Tianyi Gou <tgou@codeaurora.org>