apparmor: Fix incorrect profile->signal range check

The check on profile->signal is always false, the value can never be
less than 1 *and* greater than MAXMAPPED_SIG. Fix this by replacing
the logical operator && with ||.

Fixes: 84c455de ("apparmor: add support for profiles to define the kill signal")
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>