msm: clock-rpm: Make rpm clocks sleeping clocks

Now that we have clk_prepare/unprepare we can make the RPM clocks
sleepable. This allows us to move the sometimes costly busy wait
that RPM clocks incur when enabling and disabling or changing
rates.

Change-Id: Iab1eb0055f830e50926e198ffbfd8a9063e8ea26
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>