net/mlx5: Remove useless IPsec device checks

The mlx5_is_ipsec_device() check was to distinguish ConnectX device
related ops from FPGA, so post removing FPGA IPsec code this check
can be removed as no other device implements it.

It is safe to do it as there is already embedded check of IPsec device
in mlx5_accel_ipsec_device_caps().

Link: https://lore.kernel.org/r/e45362abfcabe18e8af20ec8d1acdc99355978f3.1649232994.git.leonro@nvidia.com


Reviewed-by: Raed Salem <raeds@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>