net/mlx5: fix meter statistics

net/mlx5: fix meter statistics

Currently, packets after meter will be steered to a global policer
table,
which includes green/red color rules for every meter, so as to have
counter statistics of each color in every meter.

There's a bug that all the rules in global policer table are matching
only color criteria, so all packets will be counted to one meter only,
and other meter statistics are always zero.

This patch does these:
1. The rules in policer table matches both meter index and color, so
packet after meter could be counted to the correct meter counter.
2. The meter index and flow index are now sharing the available
register bits dynamically. Meter index starts from lsb, and flow
index starts from msb.

Fixes: 46a5e6bc6a85 ("net/mlx5: prepare meter flow tables")
Cc: stable@dpdk.org
Signed-off-by: Shun Hao <shunh@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>