greybus: tracing: eliminate "location" comments

Each message event has a set of comments preceeding its definition.
One of them, "location", indicates where that event is used.  I
am certain that this comment will become out of date very easily.
Hopefully just the name of the event is a good enough suggestion
about where it will be used.

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>