RDMA/core: Replace the ib_port_data hw_stats pointers with a ib_port pointer

It is much saner to store a pointer to the kobject structure that contains
the cannonical stats pointer than to copy the stats pointers into a public
structure.

Future patches will require the sysfs pointer for other purposes.

Link: https://lore.kernel.org/r/f90551dfd296cde1cb507bbef27cca9891d19871.1623427137.git.leonro@nvidia.com


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