ARM: dts: msm: add a VDD_MMCX Turbo level proxy request for Kona

Add proxy-consumer properties to the VDD_MMCX rpmh-regulator
device node so that VDD_MMCX is kept enabled starting from
early in the application processor's boot sequence.  This
avoids issues when accessing multimedia clock controller
registers at initialization time.

Change-Id: I259f5bfa90737b25a372580d3889b7d42b52d459
Signed-off-by: David Collins <collinsd@codeaurora.org>