gianfar: Enable device wakeup when appropriate

The wol_en flag is 0 by default anyway, and we have the
following inconsistency: a MAGIC packet wol capable eth
interface is registered as a wake-up source but unable
to wake-up the system as wol_en is 0 (wake-on flag set to 'd').
Calling set_wakeup_enable() at netdev open is just redundant
because wol_en is 0 by default.
Let only ethtool call set_wakeup_enable() for now.

The bflock is obviously obsoleted, its utility has been corroded
over time.  The bitfield flags used today in gianfar are accessed
only on the init/ config path, with no real possibility of
concurrency - nothing that would justify smth. like bflock.

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