net/mlx5: Fix PPLM register mapping

Add reserved mapping to cover all the register in order to avoid
setting arbitrary values to newer FW which implements the reserved
fields.

Fixes: a58837f ("net/mlx5e: Expose FEC feilds and related capability bit")
Signed-off-by: Aya Levin <ayal@nvidia.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

include/linux/mlx5/mlx5_ifc.h

@@ -8835,6 +8835,8 @@ struct mlx5_ifc_pplm_reg_bits {
 
 	u8         fec_override_admin_100g_2x[0x10];
 	u8         fec_override_admin_50g_1x[0x10];
+
+	u8         reserved_at_140[0x140];
 };
 
 struct mlx5_ifc_ppcnt_reg_bits {