ethtool: fix incorrect tx-checksumming settings reporting

Currently, ethtool feature mask for checksum command is ORed with
NETIF_F_FCOE_CRC_BIT, which is bit's position number, instead of the
actual feature bit - NETIF_F_FCOE_CRC.

The invalid bitmask here might affect unrelated features when toggling
TX checksumming. For example, TX checksumming is always mistakenly
reported as enabled on the netdevs tested (mlx5, virtio_net).

Fixes: f70bb065 ("ethtool: update mapping of features to legacy ioctl requests")
Signed-off-by: Vladyslav Tarasiuk <vladyslavt@mellanox.com>
Reviewed-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>