greybus: tracing: define events using macros

A tracepoint event is defined with TP_PROTO() and TP_ARGS macros
that match that of the event's class.  A lot of repetition (and
opportunity for inadvertent errors) in tracepoint event definitions
can be eliminated by using a macro.  Define and use class-specific
event definition macros for gb_message and gb_host_device class
events.

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>