bpf_progs: use macros for kernel version

Generated via:
  for f in bpf_progs/{block,dscpPolicy,netd,offload,test}.c; do
    sed -i -r 's@KVER[(]([45]), ([0-9]+), 0[)]@KVER_\1_\2@g' "${f}"
  done

Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I8f211e47bf259fc75aa1caaaf82f41c1929ceab2