leds: ledtrig-backlight: Fix checkpatch error

Fixes the following checkpatch error:
ERROR: space prohibited before that ':' (ctx:WxE)
Signed-off-by: NSachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: NBryan Wu <cooloney@gmail.com>

drivers/leds/ledtrig-backlight.c

@@ -40,7 +40,7 @@ static int fb_notifier_callback(struct notifier_block *p,
 	int new_status = *blank ? BLANK : UNBLANK;
 
 	switch (event) {
-	case FB_EVENT_BLANK :
+	case FB_EVENT_BLANK:
 		if (new_status == n->old_status)
 			break;