greybus: connection: add trace events before disabling connection

This is what we are doing elsewhere:
- Send enable/create trace events after enabling/creating stuff.
- Send disable/remove trace events before disabling/removing stuff.

This wasn't followed in a same way while disabling connections. Fix it.

Compile tested.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>