staging: rtl8192u: move debug stuff to its own file

This is to prepare for moving them to debugfs and fix rmmod warn issue
when wlan0 is renamed to something else.

Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Tong Zhang <ztong0001@gmail.com>
Link: https://lore.kernel.org/r/20220730033335.74153-2-ztong0001@gmail.com


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