gianfar: Enable eTSEC-A002 erratum w/a for all parts

gianfar: Enable eTSEC-A002 erratum w/a for all parts

A002 is still in "no plans to fix" state, and applies to all
the current P1/P2 parts as well, so it's resonable to enable
its workaround by default, for all the soc's with etsec.
The impact of not enabling this workaround for affected parts
is that under certain conditons (runt frames or even frames
with RX error detected at PHY level) during controller reset,
the controller might fail to indicate Rx reset (GRS) completion.

Signed-off-by: Claudiu Manoil <claudiu.manoil@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>