tc: fq_codel: add drop_batch parameter

Commit 9d18562a2278 ("fq_codel: add batch ability to fq_codel_drop()")
added the new TCA_FQ_CODEL_DROP_BATCH_SIZE parameter, set by default to 64.

Add to tc command the ability to get/set the drop_batch

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>