via the DEFAULTS kernel configs. This allows folks to turn it that option
off in the kernel configs if desired without having to hack the source.
This is especially useful since PUC_FASTINTR hangs the kernel boot on my
ultra60 which has two uart(4) devices hung off of a puc(4) device.
I did not enable PUC_FASTINTR by default on powerpc since powerpc does not
currently allow sharing of INTR_FAST with non-INTR_FAST like the other
archs.
'device npx' (both of which aren't really optional right now) and
'device io' and 'device mem' (to preserve POLA for 4.x users upgrading
to 6.0) from GENERIC into DEFAULTS.
Requested by: scottl
Reviewed by: scottl
