MIPS: seccomp: Support compat with both O32 and N32

Previously the seccomp would only support strict mode on O32 userland
programs when the kernel had support for both O32 and N32 ABIs. Remove
kludge and support both ABIs.

With this patch in place, the seccomp_bpf self test now passes
global.mode_strict_support with N32 userland.

Suggested-by: Paul Burton <paul.burton@imgtec.com>
Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: IMG-MIPSLinuxKerneldevelopers@imgtec.com
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12917/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>