r8152: reduce the number of Tx

Because the Tx has the features of stopping queue and aggregation,
We don't need many tx buffers. Change the tx number from 10 to 4
to reduce the usage of the memory. This could save 16K * 6 bytes
memory.
Signed-off-by: Hayes Wang <hayeswang@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/r8152.c

@@ -424,7 +424,7 @@ enum rtl_register_content {
 	FULL_DUP	= 0x01,
 };
 
-#define RTL8152_MAX_TX		10
+#define RTL8152_MAX_TX		4
 #define RTL8152_MAX_RX		10
 #define INTBUFSIZE		2
 #define CRC_SIZE		4