ath9k: Fix LED configuration

On some x86 platforms, the LED gpio is active high
instead of active low. Identify such cards and modify
the GPIO usage to make sure LED works properly.

Cc: Russell Hu <rhu@qca.qualcomm.com>
Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>