ath9k: Fix LED polarity for some Mini PCI AR9220 MB92 cards.

The Wistron DNMA-92 and Compex WLM200NX have inverted LED polarity
(active high instead of active low).

The same PCI Subsystem ID is used by both cards, which are based on
the same Atheros MB92 design.

Cc: <linux-wireless@vger.kernel.org>
Cc: <ath9k-devel@qca.qualcomm.com>
Cc: <ath9k-devel@lists.ath9k.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Vittorio Gambaletta <linuxbugs@vittgam.net>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>