ALSA: hda/realtek: Restrict prompt only for CONFIG_EXPERT

ALSA: hda/realtek: Restrict prompt only for CONFIG_EXPERT

The split of Realtek HD-audio codec driver may cause confusions
especially when migrating from the previous kernel configurations
because it's hard to know which driver to be enabled.
Although we've already set default=y for those codec drivers, it may
still make people changing the stuff unnecessarily without knowing its
side effect.

This patch is for avoiding such pitfalls by marking the prompt of each
Realtek codec driver with CONFIG_EXPERT.  For "normal" users (that is,
unless CONFIG_EXPERT is set), all Realtek HD-audio codecs are enabled
together with CONFIG_SND_HDA_CODEC_REALTEK; this is the very same
situation like the previous kernels, after all.

For users who really care about the minimalistic configuration, they
can turn each driver on/off individually after setting
CONFIG_EXPERT=y.

The patch also adds the missing help text to the top-level
CONFIG_SND_HDA_CODEC_REALTEK together with the explanation of
individual choices, too.

Fixes: aeeb85f26c3b ("ALSA: hda: Split Realtek HD-audio codec driver")
Link: https://lore.kernel.org/10172c80-daec-4e20-ab57-a483cf1afc02@molgen.mpg.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20250806192541.21949-2-tiwai@suse.de