net/mlx5e: Use U8_MAX instead of hard coded magic number

Replace hard coded 255 magic number with U8_MAX (the register field is 8
bits).

Signed-off-by: Gal Pressman <gal@nvidia.com>
Reviewed-by: Nimrod Oren <noren@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/1764498334-1327918-4-git-send-email-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: gal-pressman

drivers/net/ethernet/mellanox/mlx5/core/en_dcbnl.c

@@ -614,8 +614,8 @@ static int mlx5e_dcbnl_ieee_setmaxrate(struct net_device *netdev,
 
 	memset(max_bw_value, 0, sizeof(max_bw_value));
 	memset(max_bw_unit, 0, sizeof(max_bw_unit));
-	upper_limit_100mbps = 255 * MLX5E_100MB;
-	upper_limit_gbps = 255 * MLX5E_1GB;
+	upper_limit_100mbps = U8_MAX * MLX5E_100MB;
+	upper_limit_gbps = U8_MAX * MLX5E_1GB;
 
 	for (i = 0; i <= mlx5_max_tc(mdev); i++) {
 		if (!maxrate->tc_maxrate[i]) {