acer-wmi: Add acpi_backlight=video quirk for the Acer KAV80

The acpi-video backlight interface on the Acer KAV80 is broken, and worse
it causes the entire machine to slow down significantly after a suspend/resume.

Blacklist it, and use the acer-wmi backlight interface instead. Note that
the KAV80 is somewhat unique in that it is the only Acer model where we
fall back to acer-wmi after blacklisting, rather then using the native
(e.g. intel) backlight driver. This is done because there is no native
backlight interface on this model.

BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1128309
Cc: stable@vger.kernel.org
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>

drivers/platform/x86/acer-wmi.c

@@ -579,6 +579,17 @@ static const struct dmi_system_id video_vendor_dmi_table[] __initconst = {
 			DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 5741"),
 		},
 	},
+	{
+		/*
+		 * Note no video_set_backlight_video_vendor, we must use the
+		 * acer interface, as there is no native backlight interface.
+		 */
+		.ident = "Acer KAV80",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "KAV80"),
+		},
+	},
 	{}
 };