The original patch adding the example used _DSC Name when Method was
intended. Fix this.

Also replace spaces used for indentation with tabs in the example.

Fixes: ed66f12b ("Documentation: ACPI: Document _DSC object usage for enum power state")
Reported-by: Bingbu Cao <bingbu.cao@intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>