greybus: tracing: add timing traces

Bryan reports he used certain message traces to determine when time
sync messages transit the boundary between the Greybus core and the
host device.  This patch adds two trace events--one a message event
for outbound messages (because it indicates its operation and its
destination), and one host device event for incoming messages
(because message information isn't available as early as desired).
These events are being created to allow the same sort of analysis
of messages without having to store extra information for every
message trace.  (The next patch changes the information a message
trace records.)

Signed-off-by: Alex Elder <elder@linaro.org>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>