rename BPF_FD_TO_INT() macro to BPF_FD_TO_U32() am: 38fb4300fb am: f0010f5901

Original change: https://android-review.googlesource.com/c/platform/system/bpf/+/1514873

Change-Id: I1c0976fb545d930991b2ceb01d26a8864e157de5