net/mlx5e: kTLS, Fix build time constant test in RX

Use the correct constant (TLS_DRIVER_STATE_SIZE_RX) in the comparison
against the size of the private RX TLS driver context.

Fixes: 1182f365 ("net/mlx5e: kTLS, Add kTLS RX HW offload support")
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>