Networking: Remove field d_sndata from the device structure. It is the same as d_appdata and unnecessary

net/devif/devif_iobsend.c

@@ -103,13 +103,13 @@ void devif_iob_send(FAR struct net_driver_s *dev, FAR struct iob_s *iob,
 
   /* Copy the data from the I/O buffer chain to the device buffer */
 
-  iob_copyout(dev->d_snddata, iob, len, offset);
+  iob_copyout(dev->d_appdata, iob, len, offset);
   dev->d_sndlen = len;
 
 #ifdef CONFIG_NET_TCP_WRBUFFER_DUMP
   /* Dump the outgoing device buffer */
 
-  lib_dumpbuffer("devif_iob_send", dev->d_snddata, len);
+  lib_dumpbuffer("devif_iob_send", dev->d_appdata, len);
 #endif
 }
 

net/devif/devif_pktsend.c

@@ -87,7 +87,7 @@
  *   an xmit or poll request from the the network interface driver.
  *
  *   This is almost identical to calling devif_send() except that the data to
- *   be sent is copied into dev->d_buf (vs. dev->d_snddata), since there is
+ *   be sent is copied into dev->d_buf (vs. dev->d_appdata), since there is
  *   no header on the data.
  *
  * Assumptions:

net/devif/devif_send.c

@@ -96,6 +96,6 @@ void devif_send(struct net_driver_s *dev, const void *buf, int len)
 {
   DEBUGASSERT(dev && len > 0 && len < NET_DEV_MTU(dev));
 
-  memcpy(dev->d_snddata, buf, len);
+  memcpy(dev->d_appdata, buf, len);
   dev->d_sndlen = len;
 }