ath9k: enable LED pin for AR946/8x chipsets

now the LED starts working for AR946/8x chipsets

Cc: "Balasubramanian, senthilkumar" <senthilb@qca.qualcomm.com>
Signed-off-by: Mohammed Shafi Shajakhan <mohammed@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>