serial: 8250_exar: switch to DEFINE_SIMPLE_DEV_PM_OPS()

serial: 8250_exar: switch to DEFINE_SIMPLE_DEV_PM_OPS()

SIMPLE_DEV_PM_OPS() is deprecated, replace it with DEFINE_SIMPLE_DEV_PM_OPS()
and use pm_sleep_ptr() for setting the driver's PM routines. We can now
remove the __maybe_unused qualifier in the suspend and resume functions.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20240219150627.2101198-6-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>