direct.conf fails to work if DirectCardName is not specified

alsa-project/alsa-ucm-conf issue #183 was opened from brndd:

The following error is produced when a card uses direct.conf but DirectCardName is not specified (with e.g. `Define { DirectCardName "UMC204HD" }`

``` $ spa-acp-tool -c 1 -vvvv info variable '${var:DirectCardName}' is not defined in this context! ```

Issue URL : https://github.com/alsa-project/alsa-ucm-conf/issues/183 Repository URL: https://github.com/alsa-project/alsa-ucm-conf