net/mlx5: Add IPoIB enhanced offloads bits to mlx5_ifc

New capability bit: ipoib_enhanced_offloads, indicates new ability for UD
QP to do RSS and enhanced IPoIB offloads and acceleration.

Add underlay_qpn to the TIS and flow_table objects In order to support
SET_ROOT command, to connect between IPoIB QPs and flow steering tables.

Signed-off-by: Erez Shitrit <erezsh@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>