asus-nb-wmi: ignore ALS notification key code

Ignore Ambient Light Sensor notification key code 0xC6 found in ASUS UX31a.
When the illuminance changes dmesg shows:
[10814.939979] asus_wmi: Unknown key c6 pressed
Signed-off-by: NViktar Vauchkevich <victorenator@gmail.com>
Signed-off-by: NMatthew Garrett <matthew.garrett@nebula.com>

drivers/platform/x86/asus-nb-wmi.c

@@ -256,6 +256,7 @@ static const struct key_entry asus_nb_wmi_keymap[] = {
 	{ KE_KEY, 0xB5, { KEY_CALC } },
 	{ KE_KEY, 0xC4, { KEY_KBDILLUMUP } },
 	{ KE_KEY, 0xC5, { KEY_KBDILLUMDOWN } },
+	{ KE_IGNORE, 0xC6, },  /* Ambient Light Sensor notification */
 	{ KE_END, 0},
 };