ath9k_htc: Reduce TX queue size

The current max queue length of 1024 is quite large
and unnecessary. 256 suffices well enough even for high
throughput situations.
Signed-off-by: Sujith Manoharan <Sujith.Manoharan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/hif_usb.h

@@ -31,7 +31,7 @@
 
 /* FIXME: Verify these numbers (with Windows) */
 #define MAX_TX_URB_NUM  8
-#define MAX_TX_BUF_NUM  1024
+#define MAX_TX_BUF_NUM  256
 #define MAX_TX_BUF_SIZE 32768
 #define MAX_TX_AGGR_NUM 20