* Move clockvar.h (header file for generic clock code) to sys/dev/dec.
* Move if_le_dec.c with DEC padded LANCE-dma (pmax/pmax, ioasic, vax 3400)
to sys/dev/dec. Remove from sys/dev/tc.
* Declare attribute le_dec_subr in /sys/dev/dec/files.dec,
use if_le_dec.c when it's defined.
* Move IOCTL asic declaration from pmax and Alpha MD machine
files to sys/dev/tc/files.tc.
* move TurboChannel and ioasic if_le attachments from pmax and Alpha machine
config files to /sys/dev/tc/files.tc. Add le_dec_subr attribute.
* Add if_le_dec attribute to if_le_ibus (pmax ds3100 pmax) LANCE attachment.
