build failed for h8300-hms with 980315

[Jeffrey A Law]

  In message < 199803221028.MAA27330@vesuri.Helsinki.FI >you write:
  > I was building a cross compiler for h8300-hms target with 980315
  > snapshot. That failed due to apparent changes in gcc/cse.c which hadn't
  > been reflected to the h8300 port. Specifically there was a duplicate
  > default: in cse.c/rtx_cost(). With a five minutes of hacking I came up
  > with this but I'm not exactly sure whether it really fixes it as should.
Thanks.  I fixed this in a slightly different way.

jeff