Quick fix for building LINT on i386. A fix is needed on all arches and

Quick fix for building LINT on i386.  A fix is needed on all arches and
this one should also work on amd64 and sparc64.

LINT was broken in r312910 with the removal of pc98 support, by changing
the pathname in UKBD_DFLT_KEYBAP from a removed pc98 file to a nonexistent
file.

There are many bugs nearby.  Some are:
- the error is not properly detected and handled by make(1), because
  kbdcontrol(8) exits with status 0 after failing to find the keymap file
- UKBD_DFLT_KEYBAP is supposed to be MI, and is in MI NOTES to try enforce
  this, but 5 out of 8 arches don't support it
- LINT seems to have been broken by this in only 7 out of 8 arches.  mips
  breaks test coverage instead, by killing this option in its MD NOTES.
  arm kills ukbd but that is not enough to configure an unsupported option
  used only by ukbd.