selftests/seccomp: Use bitwise instead of arithmetic operator for flags

selftests/seccomp: Use bitwise instead of arithmetic operator for flags

This silences the following coccinelle warning:

"WARNING: sum of probable bitmasks, consider |"

tools/testing/selftests/seccomp/seccomp_bpf.c:3131:17-18: WARNING: sum of probable bitmasks, consider |
tools/testing/selftests/seccomp/seccomp_bpf.c:3133:18-19: WARNING: sum of probable bitmasks, consider |
tools/testing/selftests/seccomp/seccomp_bpf.c:3134:18-19: WARNING: sum of probable bitmasks, consider |
tools/testing/selftests/seccomp/seccomp_bpf.c:3135:18-19: WARNING: sum of probable bitmasks, consider |

Fixes: 6a21cc50f0c7 ("seccomp: add a return code to trap to userspace")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zou Wei <zou_wei@huawei.com>
Link: https://lore.kernel.org/r/1586924101-65940-1-git-send-email-zou_wei@huawei.com
Signed-off-by: Kees Cook <keescook@chromium.org>