clk: Add trace events for rate requests

It is currently fairly difficult to follow what clk_rate_request are
issued, and how they have been modified once done.

Indeed, there's multiple paths that can be taken, some functions are
recursive and will just forward the request to its parent, etc.

Adding a lot of debug prints is just not very convenient, so let's add
trace events for the clock requests, one before they are submitted and
one after they are returned.

That way we can simply toggle the tracing on without modifying the
kernel code and without affecting performances or the kernel logs too
much.

Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20221018-clk-rate-request-tracing-v2-2-5170b363c413@cerno.tech
Signed-off-by: Stephen Boyd <sboyd@kernel.org>