net/mlx5_core: Remove static from local variable

The static is not required and breaks re-entrancy if it will be required.

Fixes: 25302363 ("net/mlx5_core: Flow steering tree initialization")
Signed-off-by: Eli Cohen <eli@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>