ARM: dts: msm: limit minimum VDD_CX active set request to SVS for msm8992

Modify the pm8994_s1_corner_ao regulator device properties in
order to enforce a minimum application processor active-set
request for VDD_CX of enabled at SVS corner.  Physically, VDD_CX
must be enabled and at a minimum of the SVS level any time that
the application processor is active.  Therefore, there is no
increase in power by enforcing this minimum within the
application processor.

Specifying this minimum ensures that software can avoid sending
RPM SMD requests for VDD_CX which do not impact the hardware
state.  This in turn reduces the latency and thus power
consumption in some use cases.  One such case is resuming from
RPM assisted power collapse to service an interrupt and then
going back to power collapse.

Also add a proxy consumer request for the highest corner which is
removed after other VDD_CX consumers have a chance to make their
own requests.

Change-Id: I8b43ef1b82d1590d6b721b8040d5bd22d678e2b1
Signed-off-by: David Collins <collinsd@codeaurora.org>