RDMA/mlx5: Drop crypto flow steering API

The mlx5 flow steering crypto API was intended to be used in FPGA
devices, which is not supported for years already. The removal of
mlx5 crypto FPGA code together with inability to configure encryption
keys makes the low steering API completely unusable.

So delete the code, so any ESP flow steering requests will fail with
not supported error, as it is happening now anyway as no device support
this type of API.

Link: https://lore.kernel.org/r/634a5face7734381463d809bfb89850f6998deac.1649232994.git.leonro@nvidia.com
Reviewed-by: Raed Salem <raeds@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>