ath9k: Pass context to ath9k_chanctx_wake_queues()

Change the ath9k_chanctx_wake_queues() API so
that we can pass the channel context that needs its
queues to be stopped.

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