adjust sanity check on sz before adding null terminator

Author: JacobBarthelmeh

src/wolfscp.c

@@ -1089,7 +1089,7 @@ static int ScpCheckForRename(WOLFSSH* ssh, int cmdSz)
     int  sz = (int)WSTRLEN(ssh->scpBasePath);
     int  idx;
 
-    if (sz > (int)sizeof(buf)) {
+    if (sz >= DEFAULT_SCP_MSG_SZ) {
         return WS_BUFFER_E;
     }