ath9k_hw: add pcieSerDesWrite to disable SERDES ASPM tweaks

This can be useful during testing of new ASPM tweaks which often
have to be done through the PCI Serializer-Deserializer (SERDES).

Cc: Aeolus Yang <aeolus.yang@atheros.com>
Cc: Madhan Jaganathan <madhan.jaganathan@atheros.com>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/hw.h b/drivers/net/wireless/ath/ath9k/hw.h
index 6c6d47b..e9578a4 100644
--- a/drivers/net/wireless/ath/ath9k/hw.h
+++ b/drivers/net/wireless/ath/ath9k/hw.h
@@ -235,6 +235,7 @@
 	int ack_6mb;
 	u32 cwm_ignore_extcca;
 	u8 pcie_powersave_enable;
+	bool pcieSerDesWrite;
 	u8 pcie_clock_req;
 	u32 pcie_waen;
 	u8 analog_shiftreg;