ath9k: Add WoW related mac80211 callbacks

add suspend/resume/set_wakeup callbacks to the driver

*suspend

- bail out only if all the conditions for configuring WoW.
  is fine, currently multivif case is not handled
- check for associated state.
- map wow triggers from user space data.
- add deauth/disassoc pattern and user defined pattern,
  for the later a list is maintained.
- store the interrupt mask before suspend, enabled beacon
  miss interrupt for WoW.
- configure WoW in the hardware by calling ath9k_hw_wow_enable.

*resume

- restore the interrupts based on the interrupt mask
  stored before suspend.
- call ath9k_hw_wow_wakeup to configure/restore the hardware.
- after wow wakeup clear away WoW events and query the
  WoW wakeup reason from the status register

*set_wakeup

- to call 'device_set_wakeup_enable' from cfg80211/mac80211
  when wow is configured and as per Rafael/Johannnes the
  right way to do so rather in the driver suspend/resume
  call back

Cc: Senthil Balasubramanian <senthilb@qca.qualcomm.com>
Cc: Rajkumar Manoharan <rmanohar@qca.qualcomm.com>
Cc: vadivel@qca.qualcomm.com
Signed-off-by: Mohammed Shafi Shajakhan <mohammed@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>