platform/x86: dell-wmi-base: Handle electronic privacy screen on/off events

platform/x86: dell-wmi-base: Handle electronic privacy screen on/off events

Add handling for events for the electronic privacy screen found on some
models (e.g. Dell Latitude 7300) being toggled on/off.

Emit KEY_EPRIVACY_SCREEN_OFF / KEY_EPRIVACY_SCREEN_ON events for this so
that userspace can show the usual on-screen-display (OSD) notification for
eprivacy screen on/off to the user.

Signed-off-by: Hans de Goede <hansg@kernel.org>
Link: https://patch.msgid.link/20251020152331.52870-3-hansg@kernel.org
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>