net: group FCoE related feature flags

Michał Mirosław's patch (http://patchwork.ozlabs.org/patch/94421/) fixes the
issue (http://patchwork.ozlabs.org/patch/94188/) about not populating FCoE related
flags correctly on vlan devices. However, only NETIF_F_FCOE_CRC is part of the
NETIF_F_ALL_TX_OFFLOADS right now, where weed NETIF_F_FCOE_MTU and NETIF_F_FSO
as well.

Therefore, add NETIF_F_ALL_FCOE to indicate feature flags used by FCoE TX offloads.
These include NETIF_F_FCOE_CRC, NETIF_F_FCOE_MTU, and NETIF_F_FSO and add them to
be part of NETIF_F_ALL_TX_OFFLOADS. This would eventually make sure all FCoE needed
flags are populated properly to vlan devices.

Signed-off-by: Yi Zou <yi.zou@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>