net: mana: Use pci_name() for debugfs directory naming

In the Linux kernel, the following vulnerability has been resolved:

net: mana: Use pci_name() for debugfs directory naming

Use pci_name(pdev) for the per-device debugfs directory instead of

hardcoded "0" for PFs and pci_slot_name(pdev->slot) for VFs. The

previous approach had two issues:

1. pci_slot_name() dereferences pdev->slot, which can be NULL for VFs

in environments like generic VFIO passthrough or nested KVM,

causing a NULL pointer dereference.

2. Multiple PFs would all use "0", and VFs across different PCI

domains or buses could share the same slot name, leading to

-EEXIST errors from debugfs_create_dir().

pci_name(pdev) returns the unique BDF address, is always valid, and is

unique across the system.