clk: qcom: gdsc: Use PM clocks to control gdsc clocks

The devices within a gdsc power domain, quite often have additional
clocks to be turned on/off along with the power domain itself.
Use PM clocks to add support for this. A list of clk_hw pointers specified
per gdsc would be the clocks turned on/off on every device start/stop
callbacks.

Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>