drm/amdgpu: Suppress keypresses from ACPI_VIDEO events

Currently we return NOTIFY_DONE for any event which we don't think is
ours. However, many laptops will send more then just an ATIF event and
will also send an ACPI_VIDEO_NOTIFY_PROBE event as well. Since we don't
check for this, we return NOTIFY_DONE which causes a keypress for the
ACPI event to be propogated to userspace. This is the equivalent of
someone pressing the display key on a laptop every time there's a
hotplug event.

So, check for ACPI_VIDEO_NOTIFY_PROBE events and suppress keypresses
from them.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>