r8169: honor jumbo settings when chipset is requested to start.

Some hardware start settings implicitely assume an usual 1500 bytes mtu
that can't be guaranteed because changes of mtu may be requested both
before and after the hardware is started.

Reported-by: Tomi Orava <tomimo@ncircle.nullnet.fi>
Signed-off-by: Francois Romieu <romieu@fr.zoreil.com>
Cc: Hayes Wang <hayeswang@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>