staging: pi433: fix memory leak with using debugfs_lookup()

When calling debugfs_lookup() the result must have dput() called on it,
otherwise the memory will leak over time.  To make things simpler, just
call debugfs_lookup_and_remove() instead which handles all of the logic
at once.  This requires saving off the root directory dentry to make
creation of individual device subdirectories easier.

Cc: Paulo Miguel Almeida <paulo.miguel.almeida.rodenas@gmail.com>
Cc: Dan Carpenter <error27@gmail.com>
Cc: Sidong Yang <realwakka@gmail.com>
Cc: Liu Shixin <liushixin2@huawei.com>
Cc: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20230202141138.2291946-1-gregkh@linuxfoundation.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>