sound(4) purge candidates

I compiled the following list of PCI drivers that we could possibly
purge. I've included the drivers that have either never been referenced
in NYC*BUG dmesgd [1] or whose last reference is prior to 2010.

snd_als4000	never (only auto-loaded by snd_driver.ko)
snd_atiixp	never
snd_cmi		2004
snd_cs4281	2020 (OpenBSD), 2004 (FreeBSD)
snd_csa		2006 (as well as a single 2020 reference)
snd_emu10k1	2006
snd_envy24	never
snd_envy24ht	2018 (only reference)
snd_es137x	2004
snd_fm801	never (only auto-loaded by snd_driver.ko)
snd_neomagic	2004
snd_solo	2004
snd_spicds	never
snd_t4dwave	2004
snd_via8233	2005
snd_via82c686	2004
snd_vibes	never (only auto-loaded by snd_driver.ko)

Christos

[1] https://dmesgd.nycbug.org