ath9k: wake up chip before initializing PAPRD table

In PAPRD table initialization path we do some register read, so
make sure the chip is awake during that. Currently PAPRD is disabled.

Signed-off-by: Mohammed Shafi Shajakhan <mshajakhan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>