When a user port does not have a label in device tree, and we thus
fall back to the eth%d scheme, the proper constant to use is
NET_NAME_ENUM. See also commit e9f656b7a214 ("net: ethernet: set
default assignment identifier to NET_NAME_ENUM"), which in turn quoted
commit 685343fc3ba6 ("net: add name_assign_type netdev attribute"):
... when the kernel has given the interface a name using global
device enumeration based on order of discovery (ethX, wlanY, etc)
... are labelled NET_NAME_ENUM.
Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>