IB/mlx5: Fix 50G per lane indication

IB/mlx5: Fix 50G per lane indication

Some released FW versions mistakenly don't set the capability that 50G per
lane link-modes are supported for VFs (ptys_extended_ethernet capability
bit).

Use PTYS.ext_eth_proto_capability instead, as this indication is always
accurate. If PTYS.ext_eth_proto_capability is valid
(has a non-zero value) conclude that the HCA supports 50G per lane.

Otherwise, conclude that the HCA doesn't support 50G per lane.

Fixes: 08e8676f1607 ("IB/mlx5: Add support for 50Gbps per lane link modes")
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Aya Levin <[email protected]>
Reviewed-by: Eran Ben Elisha <[email protected]>
Reviewed-by: Saeed Mahameed <[email protected]>
Signed-off-by: Leon Romanovsky <[email protected]>
Signed-off-by: Jason Gunthorpe <[email protected]>