IB/mlx5: Report RX checksum capabilities for IPoIB

Report RX checksum capabilities when 'ipoib_enhanced_offloads'
capabilities are set and support checksum.

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>