RDMA/mlx5: Expose private query port

Expose a non standard query port via IOCTL that will be used to expose
port attributes that are specific to mlx5 devices.

The new interface receives a port number to query and returns a structure
that contains the available attributes for that port.  This will be used
to fill the gap between pure DEVX use cases and use cases where a kernel
needs to inform userspace about various kernel driver configurations that
userspace must use in order to work correctly.

Flags is used to indicate which fields are valid on return.

MLX5_IB_UAPI_QUERY_PORT_VPORT:
	The vport number of the queered port.

MLX5_IB_UAPI_QUERY_PORT_VPORT_VHCA_ID:
	The VHCA ID of the vport of the queered port.

MLX5_IB_UAPI_QUERY_PORT_VPORT_STEERING_ICM_RX:
	The vport's RX ICM address used for sw steering.

MLX5_IB_UAPI_QUERY_PORT_VPORT_STEERING_ICM_TX:
	The vport's TX ICM address used for sw steering.

MLX5_IB_UAPI_QUERY_PORT_VPORT_REG_C0:
	The metadata used to tag egress packets of the vport.

MLX5_IB_UAPI_QUERY_PORT_ESW_OWNER_VHCA_ID:
	The E-Switch owner vhca id of the vport.

Link: https://lore.kernel.org/r/6e2ef13e5a266a6c037eb0105eb1564c7bb52f23.1618743394.git.leonro@nvidia.com


Reviewed-by: Maor Gottlieb <maorg@nvidia.com>
Signed-off-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>