apparmor: Fix some kernel-doc comments

Don't use /** for non-kernel-doc comments and change function name
aa_mangle_name to mangle_name in kernel-doc comment to Remove some
warnings found by running scripts/kernel-doc, which is caused by
using 'make W=1'.

security/apparmor/apparmorfs.c:1503: warning: Cannot understand  *
 on line 1503 - I thought it was a doc line
security/apparmor/apparmorfs.c:1530: warning: Cannot understand  *
 on line 1530 - I thought it was a doc line
security/apparmor/apparmorfs.c:1892: warning: Cannot understand  *
 on line 1892 - I thought it was a doc line
security/apparmor/apparmorfs.c:108: warning: expecting prototype for
aa_mangle_name(). Prototype was for mangle_name() instead

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>