greybus: timesync: probe shouldn't complete until FrameTime sync does

Currently the probe() function contains the asynchronous() variant of
FrameTime synchronization. This patch converts to the synchronous() version
of synchronization. This is required for two reasons first a probe() cannot
reasonably be considered to be complete without successfully completing a
time synchronization for Interfaces that care about that sync. Secondly
scheduling the operation asynchronously means its possible the PM-runtime
suspend() path can execute before the async timesync operation completes.
For both reasons we want to run synchronization - synchronously.

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