When only one port type is supported, it should be read only.
We reject changing requests, even to the auto sense mode.

Fixes: 27bf91d6 ("mlx4_core: Add link type autosensing")
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Moshe Shemesh <moshe@mellanox.com>
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>