greybus: connection: add name field

Add a name field to connections that can be used in log messages.

A connection always belongs to a host-device (bus) and can be uniquely
identified by its host-device cport id, but include remote interface and
cport id nonetheless on the following format:

	<hd_cport_id>/<intf_id>:<cport_id>

The remote interface and cport id will be zero for static connections.

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