base-files: add ucidef_set_network_device_path_port function

base-files: add ucidef_set_network_device_path_port function

The already existing uci function ucidef_set_network_device_path
can be used to specify a unique PCI address to name a network interface.
However, I noticed that some NIC ports share the same PCI address
but are still distinguishable by the dev_port value of the network
interface's sysfs entry.

This commit adds a new uci function ucidef_set_network_device_path_port,
which is similar to ucidef_set_network_device_path but takes an
additional argument where the user can specify the dev_port value.
The internal function preinit_config_port loops through
all network interfaces at the given PCI address and chooses the one
where the dev_port value matches.

This was tested on an x86_64 device using a Mellanox ConnectX-3 card.

Signed-off-by: Til Kaiser <mail@tk154.de>
Link: https://github.com/openwrt/openwrt/pull/16560
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>