modules: make sysfs attribute files readable by owner only

This code goes back to the historical bitkeeper tree commit 3f7b0672086
("Module section offsets in /sys/module"), where Jonathan Corbet wanted
to show people how to debug loadable modules.

See

    https://lwn.net/Articles/88052/



from June 2004.

To expose the required load address information, Jonathan added the
sections subdirectory for every module in /sys/modules, and made them
S_IRUGO - readable by everybody.

It was a more innocent time, plus those S_IRxxx macro names are a lot
more confusing than the octal numbers are, so maybe it wasn't even
intentional.  But here we are, thirteen years later, and I'll just change
it to S_IRUSR instead.

Let's see if anybody even notices.

Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>