RDMA/cm: Move debug counters to be under relevant IB device

The sysfs layout is created by CM incorrectly presented RDMA devices with
InfiniBand link layer. Layout of such devices represents device tree of
connections. By moving CM statistics to be under relevant port of IB
device, we will fix the following issues:

 * Symlink name - It used device name instead of specific identifier.
 * Target location - It was supposed to point to PCI-ID/infiniband_cm/
   instead of PCI-ID/infiniband/
 * Target name - It created extra device file under already existing
   device folder, e.g. mlx5_0/mlx5_0
 * Crash during boot with RDMA persistent naming patches.

 sysfs: cannot create duplicate filename '/class/infiniband_cm/mlx5_0'
 CPU: 29 PID: 433 Comm: modprobe Not tainted 5.0.0-rc5+ #178
 Call Trace:
  dump_stack+0xcc/0x180
  sysfs_warn_dup.cold.3+0x17/0x2d
  sysfs_do_create_link_sd.isra.2+0xd0/0xf0
  device_add+0x7cb/0x1450
  device_create_groups_vargs+0x1ae/0x220
  device_create+0x93/0xc0
  cm_add_one+0x38f/0xf60 [ib_cm]
  add_client_context+0x167/0x210 [ib_core]
  enable_device_and_get+0x230/0x3f0 [ib_core]
  ib_register_device+0x823/0xbf0 [ib_core]
  __mlx5_ib_add+0x45/0x150 [mlx5_ib]
  mlx5_ib_add+0x1b3/0x5e0 [mlx5_ib]
  mlx5_add_device+0x130/0x3a0 [mlx5_core]
  mlx5_register_interface+0x1a9/0x270 [mlx5_core]
  do_one_initcall+0x14f/0x5de
  do_init_module+0x247/0x7c0
  load_module+0x4c2f/0x60d0
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

After this change:
[leonro@server ~]$ ls -al /sys/class/infiniband/ibp0s12f0/ports/1/
drwxr-xr-x  2 root root    0 Mar 11 11:17 cm_rx_duplicates
drwxr-xr-x  2 root root    0 Mar 11 11:17 cm_rx_msgs
drwxr-xr-x  2 root root    0 Mar 11 11:17 cm_tx_msgs
drwxr-xr-x  2 root root    0 Mar 11 11:17 cm_tx_retries

Fixes: 110cf374

 ("infiniband: make cm_device use a struct device and not a kobject.")
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>