Correct permissions on /dev/null and friends for 2.6.32

This sets the permissions on null, zero, full, random and urandom
to 666 which is needed for older kernels.  This is part of Gentoo's
40-gentoo.rules which can now be dropped from Gentoo's ebuild.

X-gentoo-Bug: 457868
X-gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=457868
Signed-off-by: Anthony G. Basile <blueness@gentoo.org>