Fix some "little" build problems, and a redundancy call to "lwip_stats.link.recv++;" in low_level_input() & ethernetif_input().

If LINK_STATS was defined, tcpip.c couldn't be build.
Even if IP_FRAG or IP_REASSEMBLY were set, ip_frag.c functions are not build.

src/api/tcpip.c

@@ -110,11 +110,7 @@ ethernet_input(struct pbuf *p, struct netif *netif)
 
   /* points to packet payload, which starts with an Ethernet header */
   ethhdr = p->payload;
-
-#if LINK_STATS
-  lwip_stats.link.recv++;
-#endif /* LINK_STATS */
-    
+  
   switch (htons(ethhdr->type)) {
     /* IP packet? */
     case ETHTYPE_IP:

src/core/ipv4/ip_frag.c

@@ -37,8 +37,6 @@
  * 
  */
 
-#if (IP_FRAG || IP_REASSEMBLY)
-
 #include <string.h>
 
 #include "lwip/opt.h"
@@ -48,6 +46,8 @@
 #include "lwip/snmp.h"
 #include "lwip/stats.h"
 
+#if (IP_FRAG || IP_REASSEMBLY)
+
 static u8_t ip_reassbuf[IP_HLEN + IP_REASS_BUFSIZE];
 static u8_t ip_reassbitmap[IP_REASS_BUFSIZE / (8 * 8) + 1];
 static const u8_t bitmap_bits[8] = { 0xff, 0x7f, 0x3f, 0x1f,

src/netif/ethernetif.c

@@ -168,7 +168,7 @@ low_level_input(struct netif *netif)
     acknowledge that packet has been read();
 
 #if ETH_PAD_SIZE
-    pbuf_header(p, ETH_PAD_SIZE);			/* reclaim the padding word */
+    pbuf_header(p, ETH_PAD_SIZE); /* reclaim the padding word */
 #endif
 
 #if LINK_STATS
@@ -229,13 +229,7 @@ ethernetif_input(struct netif *netif)
   if (p == NULL) return;
   /* points to packet payload, which starts with an Ethernet header */
   ethhdr = p->payload;
-
-#if LINK_STATS
-  lwip_stats.link.recv++;
-#endif /* LINK_STATS */
-
-  ethhdr = p->payload;
-    
+  
   switch (htons(ethhdr->type)) {
 
 #if ETHARP_TCPIP_ETHINPUT