nfp: don't keep count for free buffers delayed kick

We only kick RX free buffer queue controller every NFP_NET_FL_BATCH
(currently 16) entries.  This means that we will always kick the QC
when write ring index is divisable by NFP_NET_FL_BATCH.  There is
no need to keep counts.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>