[netdrvr] fealnx: clean up nasty mess of arch ifdefs

Clean up config/burst value arch-specific setup.

* bcrvalue only varied by its big-endian bit
* crvalue only varied for certain types of x86-32 chips

This should make fealnx quite a bit more portable, without any behavior
change.

Signed-off-by: Jeff Garzik <jgarzik@redhat.com>