LSM: Add the comment to lsm_hooks.h

Add the large comment describing the content of the
security_operations structure to lsm_hooks.h. This
wasn't done in the previous (1/7) patch because it
would have exceeded the mail list size limits.

Signed-off-by: Casey Schaufler <[email protected]>
Acked-by: John Johansen <[email protected]>
Acked-by: Kees Cook <[email protected]>
Acked-by: Paul Moore <[email protected]>
Acked-by:  Stephen Smalley <[email protected]>
Acked-by: Tetsuo Handa <[email protected]>
Signed-off-by: James Morris <[email protected]>

Author: cschaufler