ALSA: hda/realtek: Add alc256-samsung-headphone fixup

This fixes the near-silence of the headphone jack on the ALC256-based
Samsung Galaxy Book Flex Alpha (NP730QCJ). The magic verbs were found
through trial and error, using known ALC298 hacks as inspiration. The
fixup is auto-enabled only when the NP730QCJ is detected. It can be
manually enabled using model=alc256-samsung-headphone.

Signed-off-by: Matt Kramer <mccleetus@gmail.com>
Link: https://lore.kernel.org/r/3168355.aeNJFYEL58@linus


Signed-off-by: Takashi Iwai <tiwai@suse.de>