ALSA: control: Rename CONFIG_SND_CTL_VALIDATION to CONFIG_SND_CTL_DEBUG

The purpose of CONFIG_SND_CTL_VALIDATION is rather to enable the
debugging feature for the control API.  The validation is only a part
of it.  Let's rename it to be more explicit and intuitive.

While we're at it, let's advertise, give more comment to recommend
this feature for development in the kconfig help text.

Link: https://lore.kernel.org/r/20220609120219.3937-3-tiwai@suse.de


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