Fix an error in SLIP escaping

drivers/net/slip.c

@@ -355,12 +355,12 @@ static int slip_transmit(FAR struct slip_driver_s *priv)
               if (len > 0)
                 {
                   slip_write(priv, start, len);
+                }
 
-                  /* Reset */
+              /* Reset */
 
-                  start = src + 1;
-                  len   = 0;
-                }
+              start = src + 1;
+              len   = 0;
 
               /* Then send the escape sequence */