VERIFY_OCTAL_PERMISSIONS: stricter checking for sysfs perms.

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 <[email protected]>
Acked-by: Bjorn Helgaas <[email protected]> for drivers/pci/slot.c
Acked-by: Greg Kroah-Hartman <[email protected]>
Cc: Miklos Szeredi <[email protected]>
Cc: Mark Fasheh <[email protected]>
Cc: Joel Becker <[email protected]>
Signed-off-by: Rusty Russell <[email protected]>