osbuild2/device: add Parent field to Device

osbuild, starting with version 31, supports for nesting of devices,
i.e. any device can have a parent device. See osbuild commit 45d0594

Co-Authored-By: Christian Kellner <christian@kellner.me>

internal/osbuild2/device.go

@@ -4,6 +4,7 @@ type Devices map[string]Device
 
 type Device struct {
 	Type    string        `json:"type"`
+	Parent  string        `json:"parent,omitempty"`
 	Options DeviceOptions `json:"options,omitempty"`
 }