greybus: es2: add more structure to probe error handling

Add more structure to probe error handling rather than use the big
hammer and call disconnect directly.

This is needed to fix some host-device life-time issues.

Note that there was never any need to clear the USB interface data as
this will be done by driver core.

Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>