net/mlx5: call meter detach only if DR is supported

net/mlx5: call meter detach only if DR is supported

Flow metering is supported only in direct rules (DR). Currently the APIs
of meter actions create and modify are under #ifdef
HAVE_MLX5_DR_CREATE_ACTION_FLOW_METER, while detaching the meter action
is executed unconditionally. This commit adds the same ifdef to API
mlx5_flow_meter_detach().
This commit avoids compilation failure of non-Linux operating systems
which do not support DR.

Signed-off-by: Ophir Munk <ophirmu@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>