mac80211: make LED trigger names const

This is just a code cleanup, make the LED trigger names const
as they're not expected to be modified by drivers.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/p54/led.c

@@ -83,7 +83,7 @@ static void p54_led_brightness_set(struct led_classdev *led_dev,
 
 static int p54_register_led(struct p54_common *priv,
 			    unsigned int led_index,
-			    char *name, char *trigger)
+			    char *name, const char *trigger)
 {
 	struct p54_led_dev *led = &priv->leds[led_index];
 	int err;