clk: qcom: clock-cpu-8994: Sanity the clock tree on mux/divider changes

Sanity check the clock tree whenever we write to the mux
register for the A53. We read the PLL and mux registers
and calculate the rate. Then, we read the currently voted
voltage and check if it's enough. If not, we kill the system.

Change-Id: I298c6583334a14bbf44834b99de21c30579de5d9
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>