net/mlx5: check memory allocation in flow creation

net/mlx5: check memory allocation in flow creation

rte_calloc functions returns a non-null pointer in case of
success and null pointer in case of failure.

The return value should be checked and the function flow
should take that into consideration.

This patch adds a check for rte_calloc return value in function
flow_list_create.

Fixes: 84c406e74524 ("net/mlx5: add flow translate function")
Cc: stable@dpdk.org
Signed-off-by: Asaf Penso <asafp@mellanox.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>