net/mlx4_core: Use firmware driven flow steering hash mode

The Firmware dynamically changes flow steering hash configuration from covering
L2 only to "full" L2/L3/L4 mode needed.  The dynamic change allows the driver
to set hard coded hash configuration which is changed by the firmware from L2
to L2/L3/L4 when attaching the first L3/L4 flow steering rule and back to L2
when there are no more such rules.

Signed-off-by: Hadar Hen Zion <hadarh@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>