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: I766b5e15bfdb0c68011fd2a27886026f754bdefd
Signed-off-by: Yue Ma <yuem@codeaurora.org>