- Add NetBSD autoconfiguration support.
- Rearrange code slightly to minimize the number of #ifdefs.
- Don't use a structure to access CSRs. Use macros that DTRT for
the NetBSD and FreeBSD cases.
- Deal with alignment contraint on Alpha - add 2-byte padding at the
beginning of the RFA, so that the data will be 4-byte aligned, after
the 14-byte Ethernet header.
Thanks to Matthias Drochner for the testing, and David Greenman for
the feedback on the changes.