perf/benchmark: fix seccomp_unotify benchmark for 32-bit

perf/benchmark: fix seccomp_unotify benchmark for 32-bit

Commit 7d5cb68af638 (perf/benchmark: add a new benchmark for
seccom_unotify) added a reference to __NR_seccomp into perf. This is
fine as it added also a definition of __NR_seccomp for 64-bit. But it
failed to do so for 32-bit as instead of ifndef, ifdef was used.

Fix this typo (so fix the build of perf on 32-bit).

Fixes: 7d5cb68af638 (perf/benchmark: add a new benchmark for seccom_unotify)
Cc: Andrei Vagin <avagin@google.com>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20231017083019.31733-1-jirislaby@kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>