Audio policy config: remove cross-module device port name uniqueness

            <xs:selector xpath="modules/module"/>

            <xs:field xpath="@name"/>

        </xs:key>

        <xs:key name="devicePortNameGlobalKey">

            <xs:selector xpath="modules/module/devicePorts/devicePort"/>

            <xs:field xpath="@tagName"/>

        </xs:key>

        <xs:unique name="volumeTargetUniqueness">

            <xs:selector xpath="volumes/volume"/>

            <xs:field xpath="@stream"/>

                    <xs:selector xpath="mixPorts/mixPort"/>

                    <xs:field xpath="@name"/>

                </xs:unique>

                <!-- Although this key constraint is redundant with devicePortNameGlobalKey,

                     the set is used to constraint defaultOutputDevice and attachedDevice

                     to reference a devicePort of the same module. -->

                <xs:key name="devicePortNameKey">

                    <xs:selector xpath="devicePorts/devicePort"/>

                    <xs:field xpath="@tagName"/>