AM30: patch for thinko in my previous patch

[Alexandre Oliva]

The patch:

2000-04-03  Alexandre Oliva  <aoliva@cygnus.com>

        * config/tc-mn10300.c (md_pseudo_table): Use constant names.
        (md_begin): Likewise.
        (HAVE_AM33): New macro.
        (md_assemble): Use it.  Match r_regs and xr_regs only if
        HAVE_AM33.

introduced a bug in the assembler.  It would no longer recognize
instructions marked as AM30 :-(

Here's a patch.  Ok to install?  Release branch?