net/bnxt: fix stats context calculation

net/bnxt: fix stats context calculation

The required number of statistics contexts is computed as the sum
of the number of receive and transmit rings plus one for the async
completion ring. A statistics context is not actually required for
the async completion ring, so remove it from the calculation.

Fixes: bd0a14c99f65 ("net/bnxt: use dedicated CPR for async events")
Cc: stable@dpdk.org
Signed-off-by: Lance Richardson <lance.richardson@broadcom.com>
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>