kernel: usbnet: Restore usb%d naming for cdc-ethernet devices with local MAC

kernel: usbnet: Restore usb%d naming for cdc-ethernet devices with local MAC

Prior to commit https://github.com/torvalds/linux/commit/8a7d12d674ac6f2147c18f36d1e15f1a48060edf,
cdc-ethernet USB LTE modems (e.g. Quectel EC200A) were consistently named
usb0. After 8a7d12d67, devices began renaming to eth1 due to an assumption
that local MAC addresses originate exclusively from the kernel. Some
devices provide driver-assigned local MACs, causing point-to-point
interfaces with driver-set MACs to adopt eth%d names instead of usb%d.

Restore the naming exception for point-to-point devices: interfaces
without driver MACs or with driver-provided local MACs will retain the
usb%d convention. This addresses issues reported in [1] and fixed in [2].

[1] https://lore.kernel.org/all/Z00udyMgW6XnAw6h@atmark-techno.com/
[2] https://lore.kernel.org/all/20241203130457.904325-1-asmadeus@codewreck.org/

Tested-by: Ahmed Naseef <naseefkm@gmail.com>
Signed-off-by: Ahmed Naseef <naseefkm@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/17757
Signed-off-by: Robert Marko <robimarko@gmail.com>