greybus: tracing: drop "greybus" prefix

I posted this once before but it got rejected for fear it would
not be clear which messages were related to Greybus.

Every trace event currently defined for Greybus is recorded in a
function whose name begins with "gb_".  Every trace event reported
in /sys/kernel/debug/tracing/trace includes the name of the function
in which the event was recorded.

Get rid of the "greybus: " prefix in all of the Greybus trace
events.  It just takes up precious space and is not actually
helpful.  Anyone actually enabling individual trace events should
know enough about what they're doing to recognize which ones
are being enabled.

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