drivers/hid/hid-picolcd_fb: avoid world-writable sysfs files.

In line with practice for module parameters, we're adding a build-time
check that sysfs files aren't world-writable.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Bruno Prémont <bonbons@linux-vserver.org>
Acked-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-picolcd_fb.c

diff --git a/drivers/hid/hid-picolcd_fb.c b/drivers/hid/hid-picolcd_fb.c
index c930ab8..7f965e2 100644
--- a/drivers/hid/hid-picolcd_fb.c
+++ b/drivers/hid/hid-picolcd_fb.c
@@ -501,7 +501,7 @@
 	return count;
 }
 
-static DEVICE_ATTR(fb_update_rate, 0666, picolcd_fb_update_rate_show,
+static DEVICE_ATTR(fb_update_rate, 0664, picolcd_fb_update_rate_show,
 		picolcd_fb_update_rate_store);
 
 /* initialize Framebuffer device */