platform/x86: asus-wmi: Refactor error handling

Remove exit label as it is only used once from the point in code where no
cleanup is required and return can be called immediately.

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