Some systems have an ACPI video bus but not ACPI video devices with
backlight capability. On these devices brightness key-presses are
(logically) not reported through the ACPI video bus.

Change how acpi_video_handles_brightness_key_presses() determines if
brightness key-presses are handled by the ACPI video driver to avoid
vendor specific drivers/platform/x86 drivers filtering out their
brightness key-presses even though they are the only ones reporting
these presses.

Fixes: ed83c917 ("platform/x86: panasonic-laptop: Resolve hotkey double trigger bug")
Reported-and-tested-by: Stefan Seyfried <seife+kernel@b1-systems.com>
Reported-and-tested-by: Kenneth Chan <kenneth.t.chan@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220624112340.10130-2-hdegoede@redhat.com