greybus: gb-audio: Remove useless comment

Remove comment about adding start delay since it will
be done when support for A/V synchronization is added.

Signed-off-by: Mark A. Greer <mgreer@animalcreek.com>
Acked-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>