via-rhine: disable rx_copybreak on archs that don't allow unaligned DMA access

Patch to disable the rx_copybreak feature on hardware architectures that
don't allow unaligned DMA access.

#ifdef code taken from tulip_core.c.  Problem pointed out by Ivan
Kokshaysky.

Signed-off-by: Dustin Marquess <jailbird@alcatraz.fdf.net>
Cc: Francois Romieu <romieu@fr.zoreil.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>