dt-bindings: thermal: qcom: add adc-thermal monitor bindings

Add bindings for thermal monitor, part of Qualcomm PMIC5 chips. It is a
close counterpart of VADC part of those PMICs.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20210205000118.493610-2-dmitry.baryshkov@linaro.org