RDMA/mlx5: Fix query RoCE port

RDMA/mlx5: Fix query RoCE port

mlx5_is_roce_enabled returns the devlink RoCE init value, therefore it
should be used only when driver is loaded. Instead we just need to read
the roce_en field.

In addition, rename mlx5_is_roce_enabled to mlx5_is_roce_init_enabled.

Fixes: 7a58779edd75 ("IB/mlx5: Improve query port for representor port")
Link: https://lore.kernel.org/r/20210304124517.1100608-2-leon@kernel.org
Signed-off-by: Maor Gottlieb <maorg@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>