arm: dts: qcom: Add #power-domain-cells property

clock controller nodes which also support power domains (gdscs') need
to have a #power-domain-cells property. Add these for gcc and mmcc
nodes of msm8974, gcc of apq8084 and msm8916.
Also update gcc and mmcc bindings for it.

Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Andy Gross <agross@codeaurora.org>