ath9k_hw: Fix system hang when resuming from S3/S4

ath9k_hw: Fix system hang when resuming from S3/S4

commit 5b64aa72ead6f8be488d2be7af579f0d69fb7a6e upstream.

The bit 6 & 7 of AR_WA (0x4004) should be enabled only
for the chips that are supporting L0s functionality
while resuming back from S3/S4.

Enabling these bits for AR9280 is causing system hang
within a few S3/S4-resume cycles.

Cc: Jack Lee <jlee@atheros.com>
Signed-off-by: Rajkumar Manoharan <rmanoharan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>