Scatter CQE feature relies on two flags MLX5_QP_FLAG_SCATTER_CQE and
MLX5_QP_FLAG_ALLOW_SCATTER_CQE, both of them can be provided without
relation to device capability.

Relax global validity check to allow MLX5_QP_FLAG_ALLOW_SCATTER_CQE QP
flag.

Existing user applications are failing on this new validity check.

Fixes: 90ecb37a ("RDMA/mlx5: Change scatter CQE flag to be set like other vendor flags")
Fixes: 37518fa4 ("RDMA/mlx5: Process all vendor flags in one place")
Link: https://lore.kernel.org/r/20200728120255.805733-1-leon@kernel.orgReviewed-by: Artemy Kovalyov <artemyko@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>