apparmor: fix kernel-doc complaints

Correct kernel-doc notation to placate kernel-doc W=1 warnings:

security/apparmor/policy.c:439: warning: duplicate section name 'Return'
security/apparmor/secid.c:57: warning: Cannot understand  *
security/apparmor/file.c:174: warning: cannot understand function prototype: 'struct aa_perms default_perms = '

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: John Johansen <john.johansen@canonical.com>
Cc: John Johansen <john@apparmor.net>
Cc: apparmor@lists.ubuntu.com
Cc: Paul Moore <paul@paul-moore.com>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>