ARM: dts: msm: Add VADC nodes for QCS405

Clients of VADC include reading voltage phone power,
system thermistors for thermal mitigation such as
pa_therm and xo_therm. Add the supported VADC
channels for the QCS405 platforms.

Change-Id: I6476286b055f6e8fd1477ce0322cbecda3a0aa6b
Signed-off-by: Jishnu Prakash <jprakash@codeaurora.org>