Make ed driver work again.

Make ed driver work again.

isa_compat.c
  Copied from sys/i386/isa/isa_compat.c.  It includes
  sys/pc98/pc98/isa_compat.h instead of sys/i386/isa/isa_compat.h.

isa_compat.h
  Copied from sys/i386/isa/isa_compat.c.  The ed driver is registered
  in this file until pc98's ed driver is converted into new-bus style.

files.pc98
  Use sys/pc98/pc98/isa_compat.c instead of sys/i386/isa/isa_compat.c.

if_ed.c
  - Fixed the location of the include file.
  - Disalbed pnp support.