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.

Fixes: 2132b71f

 ("net/mlx5e: Advertise globaly supported FEC modes")
Signed-off-by: Aya Levin <ayal@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>