serial: 8250_dw: Re-use temporary variable for of_node

In couple of places we may re-use temporary variable instead of
dereferencing it. No functional changes intended.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20211005134529.23256-1-andriy.shevchenko@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>