greybus: connection: rename legacy init and exit functions

Rename legacy connection init and exit functions.

This is a step towards removing the legacy-protocol handling from core.

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