greybus: timesync: Bind TimeSync into Greybus

TimeSync needs to bind into Greybus in a few places.

- core.c
  To initialize its internal state and tear-down its internal state.
  To schedule a timesync to a newly added Bundle after probe() completes.

- svc.c
  To get access to the SVC and enable/disable timesync as well as
  extracting the authoritative time from the SVC to subsequently
  disseminate to other entities in the system.

- interface.c
  To get access to an Interface in order to inform APBx of timesync
  enable/disable and authoritative operations.

This patch adds those bindings into Greybus core.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Reviewed-by: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
Acked-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>