selinux: explicitly number all selinuxfs inodes

Explicitly number all selinuxfs inodes to prevent a conflict between
inodes numbered using last_ino when created with new_inode() and those
labeled explicitly.

Signed-off-by: James Carter <jwcart2@tycho.nsa.gov>
Acked-by: Eric Paris <eparis@parisplace.org>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>