Use dev_to_hdac_dev() instead of container_of().

No functional change intended.
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Link: https://lore.kernel.org/r/20200505030357.28004-1-kai.heng.feng@canonical.comSigned-off-by: Takashi Iwai <tiwai@suse.de>