Add LF to file errors

Marlin/cardreader.cpp

@@ -309,14 +309,14 @@ void CardReader::openFile(char* name, bool read, bool replace_current/*=true*/)
     else {
       SERIAL_PROTOCOLPGM(MSG_SD_OPEN_FILE_FAIL);
       SERIAL_PROTOCOL(fname);
-      SERIAL_PROTOCOLCHAR('.');
+      SERIAL_PROTOCOLPGM(".\n");
     }
   }
   else { //write
     if (!file.open(curDir, fname, O_CREAT | O_APPEND | O_WRITE | O_TRUNC)) {
       SERIAL_PROTOCOLPGM(MSG_SD_OPEN_FILE_FAIL);
       SERIAL_PROTOCOL(fname);
-      SERIAL_PROTOCOLCHAR('.');
+      SERIAL_PROTOCOLPGM(".\n");
     }
     else {
       saving = true;