security/apparmor/lsm.c: set debug messages

Add the _APPARMOR substring to reference the intended Kconfig option.

Signed-off-by: Valentin Rothberg <valentinrothberg@gmail.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>