Revert "ath: ath9k: use debugfs_create_devm_seqfile() helper for seq_file entries"

This reverts commit d32394fa.

It has been reported to cause problems, Jeremiah writes:
	On an Acer C720 laptop if a suspend is performed the screen
	freezes, the machine locks up, and according to the indicator
	lights it does not enter suspend.  A hard reset is required to
	get it running again.

Reported-by: Jeremiah Mahler <jmmahler@gmail.com>
Cc: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>