net/mlx5: Report enhanced capabilities for IPoIB

Report 'ipoib_enhanced_offloads' capabilities from
the core layer, it will be used in the next patch from this series.

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