net: ethernet: aquantia: Superfluous initialization of "err".

Fixed superfluous initialization of err.

Signed-off-by: Pavel Belous <pavel.belous@aquantia.com>
Reviewed-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Signed-off-by: David S. Miller <davem@davemloft.net>