RDMA: Change ops->init_port to ops->port_groups

init_port was only being used to register sysfs attributes against the
port kobject. Now that all users are creating static attribute_group's we
can simply set the attribute_group list in the ops and the core code can
just handle it directly.

This makes all the sysfs management quite straightforward and prevents any
driver from abusing the naked port kobject in future because no driver
code can access it.

Link: https://lore.kernel.org/r/114f68f3d921460eafe14cea5a80ca65d81729c3.1623427137.git.leonro@nvidia.com
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

RDMA/core: Expose the ib port sysfs attribute machinery

Other things outside the core code are creating attributes against the
port. This patch exposes the basic machinery to do this.

The ib_port_attribute type allows creating groups of attributes attatched
to the port and comes with the usual machinery to do this.

Link: https://lore.kernel.org/r/5c4aeae57f6fa7c59a1d6d1c5506069516ae9bbf.1623427137.git.leonro@nvidia.com
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>