net/mlx5: fix memory region cache init

net/mlx5: fix memory region cache init

MR cache init takes place on the device configuration.
When the device is re-configured multiple times, for example when
changing the number of queue on the flight, deadlock can happen.

This patch moved MR cache init from device configuration function to
probe function to make sure init only once.

Fixes: 974f1e7ef146 ("net/mlx5: add new memory region support")

Signed-off-by: Xueming Li <xuemingl@mellanox.com>
Acked-by: Yongseok Koh <yskoh@mellanox.com>