ARM: dts: msm: allow VDD_CX to operate in AUTO mode for MSM8974Pro

The VDD_CX supply on MSM8974Pro boards is powered by a regulator
that can support high enough current to operate safely in AUTO
mode without notification of special cases from the application
processor.  Therefore, modify the VDD_CX regulator device tree
nodes for MSM8974Pro boards so that a request is sent to the RPM
with ssmd=0 in order to allow VDD_CX to operate in AUTO mode.

For MSM8974Pro + PM8941 + PM8841 boards, VDD_CX is supplied by
PM8841 SMPS 2.  For MSM8974Pro + PMA8084 boards, VDD_CX is
supplied by PMA8084 SMPS 2.

Change-Id: If5314125b7081774d5b15657e3a012cbe0ba645c
Signed-off-by: David Collins <collinsd@codeaurora.org>