shared/seccomp-util: address family filtering is broken on ppc

This reverts the gist of da1921a5 and
0d9fca76 (for ppc).

Quoting #17559:
> libseccomp 2.5 added socket syscall multiplexing on ppc64(el):
> https://github.com/seccomp/libseccomp/pull/229
>
> Like with i386, s390 and s390x this breaks socket argument filtering, so
> RestrictAddressFamilies doesn't work.
>
> This causes the unit test to fail:
> /* test_restrict_address_families */
> Operating on architecture: ppc
> Failed to install socket family rules for architecture ppc, skipping: Operation canceled
> Operating on architecture: ppc64
> Failed to add socket() rule for architecture ppc64, skipping: Invalid argument
> Operating on architecture: ppc64-le
> Failed to add socket() rule for architecture ppc64-le, skipping: Invalid argument
> Assertion 'fd < 0' failed at src/test/test-seccomp.c:424, function test_restrict_address_families(). Aborting.
>
> The socket filters can't be added so `socket(AF_UNIX, SOCK_DGRAM, 0);` still
> works, triggering the assertion.

Fixes #17559.