ASoC: omap-abe-twl6040: fix typo in bindings documentation

Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Acked-by: Peter Ujfalusi <perter.ujfalusi@ti.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>