install/kms: add modules that implement the privacy screen interface

Created by: @nl6720

https://lore.kernel.org/intel-gfx/20210421204804.589962-1-hdegoede%40redhat.com/ says that

privacy screen is actually controlled by some vendor specific ACPI/WMI interface which has a driver under drivers/platform/x86

As there's also /drivers/platform/chrome/chromeos_privacy_screen, so it is actually the whole /drivers/platform/.

A proper fix would be to add modules that depend on the drm_privacy_screen_register symbol, but mkinitcpio does not implement such functionality. See #132 (closed).

Since adding all modules with "acpi", "privacy" or "wmi" in their filename would be excessive, for now, hardcode the two privacy screen modules (thinkpad_acpi and chromeos_privacy_screen).

Fixes FS#72964.