ath9k: Fix ASPM workaround usage

The PCIE Workaround register (AR_WA/0x4004) is used to handle
various hardware quirks. For AR9002 chips, AR_WA_D3_L1_DISABLE
is used to prevent the HW from automatically entering L1 state
when D3 is enforced.

AR_WA_D3_L1_DISABLE has to be enabled for a few AR9280 based
cards, mark them based on their PCI subdevice/subvendor IDs
and enforce it in ar9002_hw_configpcipowersave().

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