net/mlx4: fix creation of flow rule w/o ETH spec

net/mlx4: fix creation of flow rule w/o ETH spec

The original commit enabled the creation of flow rule with empty
ETH address and with specific VLAN.
It works fine on PF, but such flow rule is still rejected on VF due
to kernel limitation, which blocks MAC address of all zeroes.

This patch complements the original commit.
It sets byte 0 of MAC address to 0xFF.

Fixes: c0d239263156 ("net/mlx4: support flow w/o ETH spec and with VLAN")

Signed-off-by: Dekel Peled <dekelp@mellanox.com>
Acked-by: Shahaf Shuler <shahafs@mellanox.com>