ASoC: rsnd: Drop unit-addresses without reg properties

Nodes without reg properties must not have unit addresses:

    Warning (unit_address_vs_reg): Node .../rcar_sound,dvc/dvc@0 has a unit name, but no reg property

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Mark Brown <broonie@kernel.org>