kmscompositemixer: Replace KmsCompositeMixerPortData for KmsGenericStructure
kmscompositemixer: Replace KmsCompositeMixerPortData for KmsGenericStructure

Change-Id: I1ea6bdb74089c93db98ec597893c0a048be78273

Kurento/kms-elements,Kurento/kms-elements,Kurento/kms-elements