selftests/bpf: Fix incorrect ASSERT in the tcp_hdr_options test

This patch fixes the incorrect ASSERT test in tcp_hdr_options during
the CHECK to ASSERT macro cleanup.

Fixes: 3082f8cd ("selftests/bpf: Convert tcp_hdr_options test to ASSERT_* macros")
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Wang Yufen <wangyufen@huawei.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20221107230420.4192307-3-martin.lau@linux.dev