net: arcnet: com20020: Fix null-ptr-deref in com20020pci_probe()

During driver initialization, the pointer of card info, i.e. the
variable 'ci' is required. However, the definition of
'com20020pci_id_table' reveals that this field is empty for some
devices, which will cause null pointer dereference when initializing
these devices.

The following log reveals it:

[    3.973806] KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f]
[    3.973819] RIP: 0010:com20020pci_probe+0x18d/0x13e0 [com20020_pci]
[    3.975181] Call Trace:
[    3.976208]  local_pci_probe+0x13f/0x210
[    3.977248]  pci_device_probe+0x34c/0x6d0
[    3.977255]  ? pci_uevent+0x470/0x470
[    3.978265]  really_probe+0x24c/0x8d0
[    3.978273]  __driver_probe_device+0x1b3/0x280
[    3.979288]  driver_probe_device+0x50/0x370

Fix this by checking whether the 'ci' is a null pointer first.

Fixes: 8c14f9c7

 ("ARCNET: add com20020 PCI IDs with metadata")
Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>