net/mlx5: optimize flow meter handle type

net/mlx5: optimize flow meter handle type

While flow attaches the meter handle, the meter id can be the unique tag
for the flow to get the meter handle. It's no need for flow to save the
pointer of the meter handle.

Save the meter id instead of pointer helps reduce the size for rte flow
structure.

As the supported maximum meter rule is 4K, uint16_t type is selected for
the meter id.

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