ath9k_htc: Implement multiple register write support

This patch adds support for writing multiple registers
in a single USB command.

Specific calls from the HW code that performs multiple
register writes would be modified to make use of this
in subsequent patches.

Signed-off-by: Sujith <Sujith.Manoharan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/wmi.c b/drivers/net/wireless/ath/ath9k/wmi.c
index f2ff18c..355e0db 100644
--- a/drivers/net/wireless/ath/ath9k/wmi.c
+++ b/drivers/net/wireless/ath/ath9k/wmi.c
@@ -101,6 +101,7 @@
 	wmi->drv_priv = priv;
 	wmi->stopped = false;
 	mutex_init(&wmi->op_mutex);
+	mutex_init(&wmi->multi_write_mutex);
 	init_completion(&wmi->cmd_wait);
 
 	return wmi;