ARM: dts: qcom: pm8941: Add vadc nodes needed to estimate an ocv

vbat_sns is needed to estimate a fairly accurate on chip voltage
and bat_therm is needed to produce an accurate percentage
from the estimated ocv.

Signed-off-by: Craig Tatlor <ctatlor97@gmail.com>
Acked-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>