samples: bpf: remove load_sock_ops in favour of bpftool

bpftool can do all the things load_sock_ops used to do, and more.
Point users to bpftool instead of maintaining this sample utility.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

samples/bpf/tcp_tos_reflect_kern.c

@@ -4,7 +4,7 @@
  *
  * BPF program to automatically reflect TOS option from received syn packet
  *
- * Use load_sock_ops to load this BPF program.
+ * Use "bpftool cgroup attach $cg sock_ops $prog" to load this BPF program.
  */
 
 #include <uapi/linux/bpf.h>