staging: rtl8192u: fix rmmod warn when device is renamed

staging: rtl8192u: fix rmmod warn when device is renamed

This driver creates 4 debug files under [devname] folder. The devname
could be wlan0 initially, however it could be renamed later to e.g.
enx00e04c00000. This will cause problem during debug file teardown since
it uses netdev->name, which is no longer wlan0. To solve this problem,
add a notifier to handle device renaming. Also note that we cannot
simply do debugfs_lookup to find out old dentry since by the time the
notifier is called, netdev->name is already changed to new name.

Reported-by: Zheyu Ma <zheyuma97@gmail.com>
Tested-by: Zheyu Ma <zheyuma97@gmail.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Tong Zhang <ztong0001@gmail.com>
Link: https://lore.kernel.org/r/20220730033335.74153-5-ztong0001@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>