example_app: increase PBUF_POOL_BUFSIZE and TCP_WND (for TLS)

mbedTLS needs the tcp receive window big enough to buffer a maximum
sized decryption fragment.

Since this config is an example only, let's just increase the sizes
to make this work by default.

Signed-off-by: Simon Goldschmidt <goldsimon@gmx.de>

examples/example_app/lwipopts.h

@@ -158,10 +158,10 @@ a lot of data that needs to be copied, this should be set high. */
 
 /* ---------- Pbuf options ---------- */
 /* PBUF_POOL_SIZE: the number of buffers in the pbuf pool. */
-#define PBUF_POOL_SIZE          160
+#define PBUF_POOL_SIZE          100
 
 /* PBUF_POOL_BUFSIZE: the size of each pbuf in the pbuf pool. */
-#define PBUF_POOL_BUFSIZE       128
+#define PBUF_POOL_BUFSIZE       256
 
 /** SYS_LIGHTWEIGHT_PROT
  * define SYS_LIGHTWEIGHT_PROT in lwipopts.h if you want inter-task protection
@@ -202,7 +202,7 @@ 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                 8096
+#define TCP_WND                 (20 * 1024)
 
 /* Maximum number of retransmissions of data segments. */
 #define TCP_MAXRTX              12