ASoC: omap: Fix typo in config option description

This fixes a typo in the description for SND_OMAP_SOC_HDMI_AUDIO.

Signed-off-by: Nik Nyby <nikolas@gnu.org>
Acked-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>