RDMA/core: Do not invoke init_port on compat devices

The driver interface cannot manipulate the sysfs of the compat device,
only of the full device so we must avoid calling the driver sysfs APIs on
compat devices.

This prevents an oops:

 Call Trace:
 dump_stack+0x5a/0x73
 kobject_init+0x74/0x80
 kobject_init_and_add+0x35/0xb0
 hfi1_create_port_files+0x6e/0x3c0 [hfi1]
 ib_setup_port_attrs+0x43b/0x560 [ib_core]
 add_one_compat_dev+0x16a/0x230 [ib_core]
 rdma_dev_init_net+0x110/0x160 [ib_core]
 ops_init+0x38/0xf0
 setup_net+0xcf/0x1e0
 copy_net_ns+0xb7/0x130
 create_new_namespaces+0x11a/0x1b0
 unshare_nsproxy_namespaces+0x55/0xa0
 ksys_unshare+0x1a7/0x340
 __x64_sys_unshare+0xe/0x20
 do_syscall_64+0x5b/0x180
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fixes: 5417783e

 ("RDMA/core: Support core port attributes in non init_net")
Reported-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Tested-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>