tcpdrop.bt: add a warning that it may not work
tcpdrop.bt: add a warning that it may not work

tcpdrop.bt attaches to kprobe:tcp_drop which is likely inlined on newer
kernels and cannot be replaced by anything else. The script will not
work on such kernels.

iovisor/bpftrace,iovisor/bpftrace,iovisor/bpftrace,iovisor/bpftrace