mellanox: mlx5: avoid uninitialized variable warning with gcc-12

gcc-12 started warning about 'tracker' being used uninitialized:

  drivers/net/ethernet/mellanox/mlx5/core/lag/lag.c: In function ‘mlx5_do_bond’:
  drivers/net/ethernet/mellanox/mlx5/core/lag/lag.c:786:28: warning: ‘tracker’ is used uninitialized [-Wuninitialized]
    786 |         struct lag_tracker tracker;
        |                            ^~~~~~~

which seems to be because it doesn't track how the use (and
initialization) is bound by the 'do_bond' flag.

But admittedly that 'do_bond' usage is fairly complicated, and involves
passing it around as an argument to helper functions, so it's somewhat
understandable that gcc doesn't see how that all works.

This function could be rewritten to make the use of that tracker
variable more obviously safe, but for now I'm just adding the forced
initialization of it.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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

@@ -783,7 +783,7 @@ static void mlx5_do_bond(struct mlx5_lag *ldev)
 {
 	struct mlx5_core_dev *dev0 = ldev->pf[MLX5_LAG_P1].dev;
 	struct mlx5_core_dev *dev1 = ldev->pf[MLX5_LAG_P2].dev;
-	struct lag_tracker tracker;
+	struct lag_tracker tracker = { };
 	bool do_bond, roce_lag;
 	int err;
 	int i;