net/mlx4_en: Fix wrong indication of Wake-on-LAN (WoL) support

net/mlx4_en: Fix wrong indication of Wake-on-LAN (WoL) support

commit c994f778bb1cca8ebe7a4e528cefec233e93b5cc upstream.

Currently when WoL is supported but disabled, ethtool reports:
"Supports Wake-on: d".
Fix the indication of Wol support, so that the indication
remains "g" all the time if the NIC supports WoL.

Tested:
As accepted, when NIC supports WoL- ethtool reports:
	Supports Wake-on: g
	Wake-on: d
when NIC doesn't support WoL- ethtool reports:
        Supports Wake-on: d
        Wake-on: d

Fixes: 14c07b1358ed ("mlx4: Wake on LAN support")
Signed-off-by: Inbar Karmy <inbark@mellanox.com>
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>