Input: psmouse - add a newline when printing 'proto' by sysfs

When I cat parameter 'proto' by sysfs, it displays as follows. It's
better to add a newline for easy reading.

root@syzkaller:~# cat /sys/module/psmouse/parameters/proto
autoroot@syzkaller:~#
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Link: https://lore.kernel.org/r/20200720073846.120724-1-wangxiongfeng2@huawei.comSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/mouse/psmouse-base.c

@@ -2042,7 +2042,7 @@ static int psmouse_get_maxproto(char *buffer, const struct kernel_param *kp)
 {
 	int type = *((unsigned int *)kp->arg);
 
-	return sprintf(buffer, "%s", psmouse_protocol_by_type(type)->name);
+	return sprintf(buffer, "%s\n", psmouse_protocol_by_type(type)->name);
 }
 
 static int __init psmouse_init(void)