device connection: Find connections also by checking the references

We can also use this API to find named references that the
device nodes have by using fwnode_property_get_reference_args()
function.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Tested-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>