ARM: 7888/1: seccomp: not compatible with ARM OABI

Make sure that seccomp filter won't be built when ARM OABI is in use,
since there is work needed to distinguish calling conventions. Until
that is done (which is likely never since OABI is deprecated), make
sure seccomp filter is unavailable in the OABI world.

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Will Drewry <wad@chromium.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>