greybus: es1, es2: hook tracepoints to hardware send/recv operations

This patch hooks tracepoints for the handoff point to/from hardware. With
these tracepoints in place we can view the time between gb_message_send and
usb_submit_urb and similarly we can view the time between cport_in_callback
and gb_message_recv_response/gb_message_recv_request

- trace_gb_host_device_send
- trace_gb_host_device_recv

It provides standard tracepoints at

/sys/kernel/debug/tracing/events/greybus/gb_host_device_send
/sys/kernel/debug/tracing/events/greybus/gb_host_device_recv

Giving outputs like

gb_host_device_recv: greybus:2-1 if_id=0000 l=10
gb_host_device_send: greybus:2-1 if_id=0000 l=10

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