net/mlx5e: Light-weight netdev open/stop

Create/destroy TIRs, TISs and flow tables upon PCI probe/remove rather
than upon the netdev ndo_open/stop.

Upon ndo_stop(), redirect all RX traffic to the (lately introduced)
"Drop RQ" and then close only the RX/TX rings, leaving the TIRs,
TISs and flow tables alive.

Signed-off-by: Achiad Shochat <achiad@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>