asus-laptop: handle keyboard backlight keys

Add support for the Fn+F3/Fn+F4 keys and map them
as KEY_KBDILLUMUP and KEY_KBDILLUMDOWN.

Signed-off-by: Corentin Chary <corentincj@iksaif.net>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/platform/x86/asus-laptop.c

@@ -301,6 +301,8 @@ static struct key_entry asus_keymap[] = {
 	{KE_KEY, 0x8A, KEY_PROG1},
 	{KE_KEY, 0x95, KEY_MEDIA},
 	{KE_KEY, 0x99, KEY_PHONE},
+	{KE_KEY, 0xc4, KEY_KBDILLUMUP},
+	{KE_KEY, 0xc5, KEY_KBDILLUMDOWN},
 	{KE_END, 0},
 };