kernel: Nuke ISA sound card support.

This removes the following modules:

snd_ad1816.ko
snd_ess.ko
snd_mss.ko
snd_sb8.ko
snd_sb16.ko
snd_sbc.ko
acpi.4: Document that HPET is enabled by default.

Comment out the section about debug.acpi.enabled because currently
there are no ACPI devices/features that are off by default and have
to be enabled.