net/mlx4_core: Prevent VF from changing port configuration

Added wrapper to the ACCESS_REG command for handling guest HW
registers access, preventing write operations, but do allow reads.

This will prevent SRIOV guests to change port PTYS configuration,
such as speed/advertised link modes.

Fixes: adbc7ac5c1 ('net/mlx4_core: Introduce ACCESS_REG CMD [...]')
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx4/cmd.c

@@ -1345,7 +1345,7 @@ static struct mlx4_cmd_info cmd_info[] = {
 		.out_is_imm = false,
 		.encode_slave_id = false,
 		.verify = NULL,
-		.wrapper = NULL,
+		.wrapper = mlx4_ACCESS_REG_wrapper,
 	},
 	/* Native multicast commands are not available for guests */
 	{