clk: qcom: cpu-sdxprairie: Add set rate notifier for APCS mux

Add notifier function for set rate which would move to a safe source before
configuring the PLL and switching back to PLL.

Change-Id: I7a36362364593ea6404459a4f628365a26d673c4
Signed-off-by: Naveen Yadav <naveenky@codeaurora.org>
Signed-off-by: Taniya Das <tdas@codeaurora.org>