net/mlx5e: Flatten the IPsec RX add rule path

Rewrote the IPsec RX add rule path to be less convoluted
and don't rely on pre-initialized variables. The code now has clean
linear flow with clean separation between error and success paths.

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