greybus: tracing: refine comments

I believe that duplicating the tracepoint name in comments prior to
the tracepoint is redundant, and doesn't add a lot of value.

I also believe that we can provide a little more information about
what exactly an event means, or when exactly it is called.

I don't claim this is a huge improvement, but it's a proposal.

Signed-off-by: Alex Elder <elder@linaro.org>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Reviewed-by: Jeffrey Carlyle <jcarlyle@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>