clk: rockchip: add pclk_pd_pmu to the list of rk3288 critical clocks

pclk_pd_pmu needs to keep running and with the upcoming gpio clock
handling this is not always the case anymore. So add it to the list
of critical clocks for now.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Lin Huang <hl@rock-chips.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>