serial: 8250_pnp: Move to struct dev_pm_ops

The established way to provide PM callbacks is through struct dev_pm_ops
which is more generic.

Convert driver to use it instead of legacy approach.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20190726172817.73253-1-andriy.shevchenko@linux.intel.com


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