Please remove all bit fields in bpf uapi

Hi, all

I'm tring to port bpf.h to Go, however it's very hard to make it right
with cgo since bit fields some fields didn't match any type of Go.

i.e.
struct bpf_prog_info {
        /* .... */
        __u32 gpl_compatible:1;             <-- boolean ?
        __u32 :31; /* alignment pad */   <--- padding with 31 ?

UAPI(User application interface) not just for GCC only right? If it's
true, I think remove all bit fields is more appropriate.

Thanks. Regards
Meng Zhuo