ath9k: Fix issues in the main btcoex timer

* ath9k_mci_update_rssi() is required only for
  cards that use MCI scheme. Make sure that it
  is not called for 3-wire cards.

* Call ath9k_ps_wakeup() early since register
  accesses are made in ath9k_mci_update_rssi().

* Fix usage of btcoex_lock to handle no_stomp_timer.

Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>