lan78xx: Fix link status notifications

The patch to allow packet reception before the first transmission broke
the notification and handling of link status changes. Move the new call
to tasklet_schedule into lan78xx_link_reset to fix it.

See: https://github.com/raspberrypi/linux/issues/2617



Fixes: d407fc22 ("net: lan78xx: fix rx handling before first packet is send")
Suggested-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Phil Elwell <phil@raspberrypi.org>