clk: qcom: clk-rcg2: Configure the RCGs to a safe frequency as needed

In certain cases, an RCG might be prone to being enabled even
though the overlying software thinks that it disabled the RCG.
In order to avoid letting the RCG go into an invalid state, support
parking it at a safe frequency during clk_disable() and deferring
all the RCG configuration updates to be done during clk_enable(),
if a scaling request comes in whilst the clock is disabled.

Change-Id: I55f1d1d346182a2b480127c57d6659fc9a63331b
Signed-off-by: Deepak Katragadda <dkatraga@codeaurora.org>