greybus: es-drivers: add outbound timestamp to connection

greybus: es-drivers: add outbound timestamp to connection

In order to facilitate grabbing a timestamp that doesn't include greybus
overhead, this patch adds a timestamp right before usb_submit_urb() for
both es1.c and es2.c. Long term the timestmaping of messages like this
probably wants to go away but, for the moment it may have some use to the
firmware people instrumenting the performance of the system.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>