net/mlx5e: fix return value check in mlx5e_ipsec_remove_trailer()

mlx5e_ipsec_remove_trailer() should return an error code if function
pskb_trim() returns an unexpected value.

Fixes: 2ac9cfe7

 ("net/mlx5e: IPSec, Add Innova IPSec offload TX data path")
Signed-off-by: Yuanjun Gong <ruc_gongyuanjun@163.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>