Update Microblaze Ethernet Lite lwipopts.h for better efficiency.

Demo/MicroBlaze_Spartan-6_EthernetLite/SDKProjects/RTOSDemo/lwIP/lwIP_Apps/lwipopts.h

@@ -204,7 +204,7 @@ a lot of data that needs to be copied, this should be set high. */
 #define TCP_MSS					1460
 
 /* TCP sender buffer space (bytes). */
-#define TCP_SND_BUF				2048
+#define TCP_SND_BUF				( TCP_MSS * 2 )
 
 /* TCP sender buffer space (pbufs). This must be at least = 2 *
    TCP_SND_BUF/TCP_MSS for things to work. */
@@ -216,7 +216,7 @@ a lot of data that needs to be copied, this should be set high. */
 #define TCP_SNDLOWAT			(TCP_SND_BUF/2)
 
 /* TCP receive window. */
-#define TCP_WND					4048
+#define TCP_WND					( PBUF_POOL_SIZE * PBUF_POOL_BUFSIZE )
 
 /* Maximum number of retransmissions of data segments. */
 #define TCP_MAXRTX				12