[PATCH] spidernet: poor network performance

Correct a problem seen on later kernels running the NetPIPE application.
Specifically, NetPIPE would begin running very slowly at the 1533 packet
size.  It was determined that Spidernet slowed with an idle DMA engine.

Signed-off-by: James K Lewis <jklewis@us.ibm.com>
Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>