net/mlx5: fix Rx CQ doorbell synchronization on aarch64

net/mlx5: fix Rx CQ doorbell synchronization on aarch64

The Rx completion queue doorbell field needs to be updated after
the last CQE decompressed. For the weaker memory model processors,
the compiler barrier is not sufficient to guarantee the order of
these operations, so use the coherent I/O memory barrier to make
sure these fields are updated in order.

Fixes: 570acdb1da8a ("net/mlx5: add vectorized Rx/Tx burst for ARM")
Cc: stable@dpdk.org
Suggested-by: Gavin Hu <gavin.hu@arm.com>
Signed-off-by: Phil Yang <phil.yang@arm.com>
Reviewed-by: Gavin Hu <gavin.hu@arm.com>
Acked-by: Matan Azrad <matan@mellanox.com>