wiznet5k: Properly enable socket buffers for W5100(S).

The W5100 and W5100S only have 4 available sockets and 16kB of socket
buffer. Allocating 16kB to either the receive or transmit buffer of a
single socket is not allowed, so the current setup does not change the
allocation for socket 0 from the reset default. ctlwizchip is returning
-1 to indicate the error, but the response isn't being inspected and
probably doesn't need to be.

Signed-off-by: Jared Hancock <jared@greezybacon.me>

extmod/network_wiznet5k.c

@@ -211,7 +211,11 @@ static void wiznet5k_init(void) {
     // Configure wiznet for raw ethernet frame usage.
 
     // Configure 16k buffers for fast MACRAW
+    #if _WIZCHIP_ < W5200
+    uint8_t sn_size[8] = {8, 0, 0, 0, 8, 0, 0, 0};
+    #else
     uint8_t sn_size[16] = {16, 0, 0, 0, 0, 0, 0, 0, 16, 0, 0, 0, 0, 0, 0, 0};
+    #endif
     ctlwizchip(CW_INIT_WIZCHIP, sn_size);
 
     if (wiznet5k_obj.use_interrupt) {