rtl8192u: Don't need to save device proc dir PDE

Don't need to save the PDE of a directory created under /proc/net/rtl8192/ as
we can use proc subtree deletion to get rid of it and all its children.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
cc: Jerry Chuang <jerry-chuang@realtek.com>
cc: linux-wireless@vger.kernel.org
cc: devel@driverdev.osuosl.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>