platform/x86: asus-wmi: Rename CHARGE_THRESHOLD to RSOC

The device is officially called "Relative state of charge" (RSOC).
At the same time add the missing DEVID from the name.

Signed-off-by: Kristian Klausen <kristian@klausen.dk>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>