MFC r347304:
Always return success for RoCE modify port in mlx5ib.

CM layer calls ib_modify_port() regardless of the link layer.

For the Ethernet ports, qkey violation and Port capabilities
are meaningless. Therefore, always return success for ib_modify_port
calls on the Ethernet ports.

Linux Commit:
ec2558796d25e6024071b6bcb8e11392538d57bf

Submitted by: slavash@
Sponsored by: Mellanox Technologies