[ Upstream commit 474a31e13a4e9749fb3ee55794d69d0f17ee0998 ]

We cannot register the same netdev notifier multiple times when probing
stmmac devices. Register the notifier only once in module init, and also
make debugfs creation/deletion safe against simultaneous notifier call.

Fixes: 481a7d154cbb ("stmmac: debugfs entry name is not be changed when udev rename device name.")
Signed-off-by: Aaro Koskinen <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>