ASoC: hdmi-codec: wire up the .prepare callback also for SPDIF DAI ops

Commit 2fef64eec23a ("ASoC: hdmi-codec: Add a prepare hook") added a
prepare implementation. Back then the new callback was only integrated
with hdmi_codec_i2s_dai_ops (which is used by the I2S input code-path).
It was not added to hdmi_codec_spdif_dai_ops (which is used by the SPDIF
input code-path).

With commit baf616647fe6 ("drm/connector: implement generic HDMI audio
helpers") the DRM subsystem has gained a helper framework which can be
used by HDMI controller drivers. HDMI controller drivers are often
tightly coupled with the hdmi-codec because of the so-called HDMI audio
infoframe (which is often managed by the display controller).

To allow the new DRM HDMI audio framework to work with the hdmi-codec
driver for SPDIF inputs we also need to hook up the prepare callback to
hdmi_codec_spdif_dai_ops. Just hooking into the hw_params callback would
not be enough as hw_params (is called too early and) doesn't have access
to the HDMI audio infoframe contents.

Suggested-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://patch.msgid.link/20250329191433.873237-1-martin.blumenstingl@googlemail.com
Signed-off-by: Mark Brown <broonie@kernel.org>