platform/x86: dell-uart-backlight: Use acpi_video_get_backlight_type()

platform/x86: dell-uart-backlight: Use acpi_video_get_backlight_type()

The dell-uart-backlight driver supports backlight control on Dell All In
One (AIO) models using a backlight controller board connected to an UART.

In DSDT this uart port will be defined as:

   Name (_HID, "DELL0501")
   Name (_CID, EisaId ("PNP0501")

Now the first AIO has turned up which has not only the DSDT bits for this,
but also an actual controller attached to the UART, yet it is not using
this controller for backlight control.

Use the acpi_video_get_backlight_type() function from the ACPI video-detect
code to check if the dell-uart-backlight driver should actually be used.
This allows reusing the existing ACPI video-detect infra to override
the backlight control method on the commandline or with DMI quirks.

Fixes: 484bae9e4d6a ("platform/x86: Add new Dell UART backlight driver")
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Link: https://patch.msgid.link/20240814190159.15650-3-hdegoede@redhat.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>