ARM: dts: msm: use a corner regulator for wcnss VDD_CX on all boards

Update wcnss nodes to use voltage corner regulators for VDD_CX on MSM8226,
MSM8610, MSM8974, and MSM8974Pro.

Also update the wcnss platform driver to use voltage corner values for the
VDD_CX regulator supply.

Change-Id: I3f42104c2609a8cd237a34c66ff76be4426e9de8
Signed-off-by: Yue Ma <yuem@codeaurora.org>