ath9k_hw: Update the PCI WAR register

This patch updates the PCI power save handling
code, fixing ASPM hangs and handling device state D3
properly.

The WAR register is programmed with the correct
values now.

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