ACPI: property: Refactor acpi_data_prop_read_single()

Refactor acpi_data_prop_read_single() for decreased indentation
and better structure. No functional changes intended.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>