RDMA/mlx5: Allow only raw Ethernet QPs when RoCE isn't enabled

RDMA/mlx5: Allow only raw Ethernet QPs when RoCE isn't enabled

When operating in switchdev mode or using devlink to disable RoCE
only raw Ethernet QPs are allowed to be created.

When in switchdev mode this can lead to passing an invalid port number
as part of the modify qp firmware cmd and will lead to a syndrome
reported back to the user, such as:

 * mlx5_cmd_check:803:(pid 50148): RST2INIT_QP(0x502) op_mod(0x0) failed,
   status bad parameter(0x3), syndrome (0x177405).

Internal UD QP might be used to test for write combining support (even if
externally we report RoCE as disabled) check for that specific flag and
allow is specifically.

Fixes: c6efc58387ce ("IB/mlx5: Add proper representors support")
Link: https://lore.kernel.org/r/20200506071602.7177-3-leon@kernel.org
Signed-off-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>