IB/mlx5: Set flow steering capability bit

Flow steering is supported by mlx5 device when the following
features are supported by firmware:

1. NIC RX flow table.
2. Device has enough flow steering levels.
3. Atomic modification of flow table entry.
4. Flow tables chaining.

To check if flow steering is supported it's enough to check
if the driver opened the mlx5 bypass namespace.

Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>