RDMA/core: Use kvzalloc when allocating the struct ib_port

RDMA/core: Use kvzalloc when allocating the struct ib_port

The 'struct attribute' flex array contains some struct lock_class_key's
which become big when lockdep is turned on. Big enough that some drivers
will not load when CONFIG_PROVE_LOCKING=y because they cannot allocate
enough memory:

 WARNING: CPU: 36 PID: 8 at mm/page_alloc.c:5350 __alloc_pages+0x27e/0x3e0
  Call Trace:
   kmalloc_order+0x2a/0xb0
   kmalloc_order_trace+0x19/0xf0
   __kmalloc+0x231/0x270
   ib_setup_port_attrs+0xd8/0x870 [ib_core]
   ib_register_device+0x419/0x4e0 [ib_core]
   bnxt_re_task+0x208/0x2d0 [bnxt_re]

Link: https://lore.kernel.org/r/20211019002656.17745-1-wangyugui@e16-tech.com
Signed-off-by: wangyugui <wangyugui@e16-tech.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>