net/mlx5: fix crash on null operation

net/mlx5: fix crash on null operation

mlx5 implements mlx5_flow_null_drv_ops to be used when a specific
flow typei/driver is not available or invalid.
This routines return error without modifying the rte_flow_error
parameter passed to them which causes testpmd, for example, to crash.
This commit addresses the issue by modifying the rte_flow_error
parameter in theses routines.

Fixes: 0c76d1c9a18d ("net/mlx5: add abstraction for multiple flow drivers")
Fixes: 684dafe795d0 ("net/mlx5: add flow query abstraction interface")
Cc: stable@dpdk.org
Signed-off-by: Moti Haimovsky <motih@mellanox.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>