msi-laptop: Port to new backlight interface selection API

Port the backlight selection logic to the new backlight interface
selection API.

This commit also removes various obsolete pr_xxx messages related to
backlight interface selection. These are obsolete because they assume
there is only a vendor or acpi backlight driver and no other choice.
Also they are not necessary, if the user wants to know which backlight
interfaces are registered a simple "ls /sys/class/backlight" suffices.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Darren Hart <dvhart@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/platform/x86/msi-laptop.c

@@ -64,6 +64,7 @@
 #include <linux/i8042.h>
 #include <linux/input.h>
 #include <linux/input/sparse-keymap.h>
+#include <acpi/video.h>
 
 #define MSI_DRIVER_VERSION "0.5"
 
@@ -1069,9 +1070,8 @@ static int __init msi_init(void)
 
 	/* Register backlight stuff */
 
-	if (!quirks->old_ec_model || acpi_video_backlight_support()) {
-		pr_info("Brightness ignored, must be controlled by ACPI video driver\n");
-	} else {
+	if (quirks->old_ec_model ||
+	    acpi_video_get_backlight_type() == acpi_backlight_vendor) {
 		struct backlight_properties props;
 		memset(&props, 0, sizeof(struct backlight_properties));
 		props.type = BACKLIGHT_PLATFORM;