HID: picoLCD: optimize for inactive debugfs

Matthieu CASTET adjusted picolcd_debug_out_report() to only operate when
there is an active listener on debugfs for events.

His change got lost while splitting hid_picolcd.c, restore it.
Signed-off-by: NBruno Prémont <bonbons@linux-vserver.org>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

drivers/hid/hid-picolcd_debugfs.c

@@ -402,7 +402,7 @@ void picolcd_debug_out_report(struct picolcd_data *data,
 #define BUFF_SZ 256
 
 	/* Avoid unnecessary overhead if debugfs is disabled */
-	if (!hdev->debug_events)
+	if (list_empty(&hdev->debug_list))
 		return;
 
 	buff = kmalloc(BUFF_SZ, GFP_ATOMIC);