IB/core: Shuffle locks in ib_port_data to save memory

pahole shows two 4-byte holes in struct ib_port_data after pkey_list_lock
and netdev_lock respectively.

Shuffling the netdev_lock to be after pkey_list_lock, this shaves off
eight bytes from the struct.

Link: https://lore.kernel.org/r/20210616154509.1047-3-anand.a.khoje@oracle.com
Suggested-by: Haakon Bugge <haakon.bugge@oracle.com>
Signed-off-by: Anand Khoje <anand.a.khoje@oracle.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>