greybus: connection: drop the svc quiescing operation

Connection tear down is being reworked, and the SVC quiescing operation
is going away.

Let's remove this operation now along with the coupled second ping from
our intermediate tear down implementation.

This both avoids unnecessary noise in the logs resulting from the fact
that the SVC side of the quiescing operation was never merged, and
speeds up connection tear down slightly.

Testing done: Tested on EVT2 using runtime PM.

Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Sandeep Patil <sspatil@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>