net/mlx5e: Make clear what IPsec rx_err does

Reuse existing struct what holds all information about modify
header pointer and rule. This helps to reduce ambiguity from the
name _err_ that doesn't describe the real purpose of that flow
table, rule and function - to copy status result from HW to
the stack.

Reviewed-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>