drm: bridge: adv7511: Enable SPDIF DAI

ADV7511 support I2S or SPDIF as audio input interfaces. This commit
enable support for SPDIF.

Signed-off-by: Bogdan Togorean <bogdan.togorean@analog.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200413113513.86091-1-bogdan.togorean@analog.com