net/mlx5e: Fix arch depending casting issue in FEC
Change type of active_fec to u32 to match the type expected by
mlx5e_get_fec_mode. Copy active_fec and configured_fec values to
unsigned long before preforming bitwise manipulations.
Take the same approach when configuring FEC over 50G link modes: copy
the policy into an unsigned long and only than preform bitwise
operations.