ASoC: hdac_hdmi: use dev_to_hdac_dev and to_ehdac_device

Use dev_to_hdac_dev() and to_ehdac_device() instead of open-coding.

Signed-off-by: Geliang Tang <geliangtang@163.com>
Reviewed-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>