gianfar: Enable eTSEC-106 erratum w/a for MPC8548E Rev2

Enable workaround for MPC8548E erratum eTSEC 106,
"Excess delays when transmitting TOE=1 large frames".
(see commit 53fad773 "gianfar: Enable eTSEC-20 erratum w/a
for P2020 Rev1")

This erratum was fixed in Rev 3.1.x.

Signed-off-by: Atsushi Nemoto <nemoto@toshiba-tops.co.jp>
Acked-by: Claudiu Manoil <claudiu.manoil@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>