linux-phytec-fsl

samples/kobject/: 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.

Cc: Greg Kroah-Hartman <greg@kroah.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>