ibm_newemac: Fix problem with jumbo frame support and EMAC V4.patch

This fixes the jumbo frame support on EMAC V4 systems. Now the correct
bit is set depending on the EMAC version configured.

Tested on Kilauea (405EX) and Canyonlands (460EX).

Signed-off-by: Stefan Roese <sr@denx.de>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>