seccomp: Add a seccomp_data parameter secure_computing()

Currently, if arch code wants to supply seccomp_data directly to
seccomp (which is generally much faster than having seccomp do it
using the syscall_get_xyz() API), it has to use the two-phase
seccomp hooks. Add it to the easy hooks, too.

Cc: linux-arch@vger.kernel.org
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>