leds: trigger: netdev: fix handling on interface rename

The NETDEV_CHANGENAME code is not "unneeded" like it is stated in commit
4cb65605 ("leds: trigger: netdev: fix refcnt leak on interface
rename").

The event was accidentally misinterpreted equivalent to
NETDEV_UNREGISTER, but should be equivalent to NETDEV_REGISTER.

This was the case in the original code from the openwrt project.

Otherwise, you are unable to set netdev led triggers for (non-existent)
netdevices, which has to be renamed. This is the case, for example, for
ppp interfaces in openwrt.

Fixes: 06f502f5 ("leds: trigger: Introduce a NETDEV trigger")
Fixes: 4cb65605

 ("leds: trigger: netdev: fix refcnt leak on interface rename")
Signed-off-by: Martin Schiller <ms@dev.tdt.de>
Signed-off-by: Pavel Machek <pavel@ucw.cz>