greybus: svc: implement connection_quiescing call

Implement Greybus remote call to connection_quiescing operation. This
operation disables flow contorl for the connection and resets associated
attributes.

Testing done: tested along with required NuttX firmware changes, booted
EVT2, inserted module, removed module, inserted module. Verified module
was functioning as expected.

Signed-off-by: Jeffrey Carlyle <jcarlyle@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>