common/mlx5: fix queue doorbell record size

common/mlx5: fix queue doorbell record size

When Rx/Tx queue was being created with DevX the allocated
doorbell record size was only uint64_t. That was definitely
less than size of CPU cacheline and it might have happened the
doorbell records attached to different queues handled by
different cores were allocated within same cacheline. It might
have caused the contention on doorbell record writing.

This patch extends the allocated memory size for doorbell
record to cacheline size.

Fixes: 21cae8580fd0 ("net/mlx5: allocate door-bells via DevX")
Cc: stable@dpdk.org
Signed-off-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>