qdev: Get just property name at error_set_from_qdev_prop_error()

qdev: Get just property name at error_set_from_qdev_prop_error()

Replace `Property *prop` parameter with `char *name`, to reduce
dependency of getter and setter functions on the Property struct
(which will be changed in following patches).

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20201211220529.2290218-19-ehabkost@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>