platform/x86: asus-wmi: Organize code into sections

The driver has grown pretty big and will grow more, which makes it hard to
navigate and understand. Add uniform comments to the code and ensure that
it is sorted into logical sections.

Signed-off-by: Yurii Pavlovskyi <yurii.pavlovskyi@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>