bpf: simplify code in btf_parse_hdr

It could directly return 'btf_check_sec_info' to simplify code.

Signed-off-by: William Dean <williamsukatube@163.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20220917084248.3649-1-williamsukatube@163.com


Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>