msm: clock: Hook into clock tracepoints

Tracepoints already exist for clk_enable(), clk_disable(), and
clk_set_rate(). Add callbacks for these tracepoints so that we
can easily trace clock operations in the kernel.

For example:
 # pwd
 /sys/kernel/debug/tracing
 # echo 1 > events/power/clock_enable/enable
 # cat trace
 <lots of clock enables>

Change-Id: I3b845653be427ff4b33bb31b5b82f73c4695d230
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>