net: Stop including NFS overhead in defragment max

At least on bfin, this "specimen" is actually allocated in the BSS and
wastes lots of memory in already tight memory conditions.

Also, with the introduction of NFSv3 support, this waste got
substantially larger.

Just remove it. If a board needs a specific different defragment size,
that board can override this setting.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>

net/net.c

@@ -834,15 +834,7 @@ int net_send_udp_packet(uchar *ether, struct in_addr dest, int dport, int sport,
 #ifndef CONFIG_NET_MAXDEFRAG
 #define CONFIG_NET_MAXDEFRAG 16384
 #endif
-/*
- * MAXDEFRAG, above, is chosen in the config file and  is real data
- * so we need to add the NFS overhead, which is more than TFTP.
- * To use sizeof in the internal unnamed structures, we need a real
- * instance (can't do "sizeof(struct rpc_t.u.reply))", unfortunately).
- * The compiler doesn't complain nor allocates the actual structure
- */
-static struct rpc_t rpc_specimen;
-#define IP_PKTSIZE (CONFIG_NET_MAXDEFRAG + sizeof(rpc_specimen.u.reply))
+#define IP_PKTSIZE (CONFIG_NET_MAXDEFRAG)
 
 #define IP_MAXUDP (IP_PKTSIZE - IP_HDR_SIZE)