net/mlx5: save meter index instead of meter id

net/mlx5: save meter index instead of meter id

Currently, while creating the flow with meter, meter id is saved to the
rte flow. While destroying the flow, the meter object will be found by
the meter id, so the meter object will be released accordingly. But as
the meter id is configured by user, while the meter id is set to 0, it
doesn't make any sense to flow destroy since 0 means flow doesn't have
meter. The meter object with id 0 will be leaked.

As meter object is allocated from indexed memory, and the index starts
from 1, save the internal generated index instead of user defined meter
id will never meet the issue as above.

This patch saves meter index instead of meter id in rte flow.

Signed-off-by: Suanming Mou <suanmingm@mellanox.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>