net: usb: asix: ax88772: re-add usbnet_link_change() in phylink callbacks

net: usb: asix: ax88772: re-add usbnet_link_change() in phylink callbacks

Commit e0bffe3e6894 ("net: asix: ax88772: migrate to phylink") replaced
the asix_adjust_link() PHY callback with phylink's mac_link_up() and
mac_link_down() handlers, but did not carry over the usbnet_link_change()
notification that commit 805206e66fab ("net: asix: fix "can't send until
first packet is send" issue") had added.

As a result, the original symptom returns: when the link comes up,
usbnet is never notified, so the RX URB submission stays dormant until
some other event (e.g. a transmitted packet triggering the status
endpoint interrupt) wakes it up.

This is reproducible with the Apple A1277 USB Ethernet Adapter
(05ac:1402, AX88772A based) on a Banana Pro using a static IPv4
configuration. After bringing the interface up, no incoming packets are
received until the first outgoing frame triggers usbnet's RX path.

Restore the link change notification, gated on a carrier transition so
the call remains idempotent if the status endpoint also reports the
change later.

Fixes: e0bffe3e6894 ("net: asix: ax88772: migrate to phylink")
Signed-off-by: Markus Baier <Markus.Baier@soslab.tu-darmstadt.de>
Tested-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://patch.msgid.link/20260501163941.107668-1-Markus.Baier@soslab.tu-darmstadt.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>