VERIFY_OCTAL_PERMISSIONS: stricter checking for sysfs perms.

Summary of http://lkml.org/lkml/2014/3/14/363 :

  Ted: module_param(queue_depth, int, 444)
  Joe: 0444!
  Rusty: User perms >= group perms >= other perms?
  Joe: CLASS_ATTR, DEVICE_ATTR, SENSOR_ATTR and SENSOR_ATTR_2?

Side effect of stricter permissions means removing the unnecessary
S_IFREG from several callers.

Note that the BUILD_BUG_ON_ZERO((perm) & 2) test was removed: a fair
number of drivers fail this test, so that will be the debate for a
future patch.

Suggested-by: Joe Perches <joe@perches.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com> for drivers/pci/slot.c
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/fs/fuse/cuse.c b/fs/fuse/cuse.c
index b96a49b..77cf5ee 100644
--- a/fs/fuse/cuse.c
+++ b/fs/fuse/cuse.c
@@ -568,7 +568,7 @@
 
 	return sprintf(buf, "%d\n", atomic_read(&cc->fc.num_waiting));
 }
-static DEVICE_ATTR(waiting, S_IFREG | 0400, cuse_class_waiting_show, NULL);
+static DEVICE_ATTR(waiting, 0400, cuse_class_waiting_show, NULL);
 
 static ssize_t cuse_class_abort_store(struct device *dev,
 				      struct device_attribute *attr,
@@ -579,7 +579,7 @@
 	fuse_abort_conn(&cc->fc);
 	return count;
 }
-static DEVICE_ATTR(abort, S_IFREG | 0200, NULL, cuse_class_abort_store);
+static DEVICE_ATTR(abort, 0200, NULL, cuse_class_abort_store);
 
 static struct attribute *cuse_class_dev_attrs[] = {
 	&dev_attr_waiting.attr,