Add the rpm clock controller node for msm8996 devices

Cc: Andy Gross <andy.gross@linaro.org>
Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
Acked-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>