RDMA/core: Allow port_groups to be used with namespaces

Now that the port_groups data is being destroyed and managed by the core
code this restriction is no longer needed. All the ib_port_attrs are
compatible with the core's sysfs lifecycle.

When the main device is destroyed and moved to another namespace the
driver's port sysfs can be created/destroyed as well due to it now being a
simple attribute list.

Link: https://lore.kernel.org/r/afd8b676eace2821692d44489ff71856277c48d1.1623427137.git.leonro@nvidia.com


Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>