platform/x86: ayaneo-ec: Add controller power and modules attributes

platform/x86: ayaneo-ec: Add controller power and modules attributes

The Ayaneo 3 features hot-swappable controller modules. The ejection
and management is done through HID. However, after ejecting the modules,
the controller needs to be power cycled via the EC to re-initialize.

For this, the EC provides a variable that holds whether the left or
right modules are connected, and a power control register to turn
the controller on or off. After ejecting the modules, the controller
should be turned off. Then, after both modules are reinserted,
the controller may be powered on again to re-initialize.

This patch introduces two new sysfs attributes:
 - `controller_modules`: a read-only attribute that indicates whether
   the left and right modules are connected (none, left, right, both).
 - `controller_power`: a read-write attribute that allows the user
   to turn the controller on or off (with '1'/'0').

Therefore, after ejection is complete, userspace can power off the
controller, then wait until both modules have been reinserted
(`controller_modules` will return 'both') to turn on the controller.

Reviewed-by: Armin Wolf <W_Armin@gmx.de>
Signed-off-by: Antheas Kapenekakis <lkml@antheas.dev>
Link: https://patch.msgid.link/20251119174505.597218-5-lkml@antheas.dev
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>