net/mlx5: E-Switch, Reduce ingress acl modify metadata stack usage

Fix the following compiler warning:
In function ‘esw_vport_add_ingress_acl_modify_metadata’:
the frame size of 1084 bytes is larger than 1024 bytes [-Wframe-larger-than=]

Since the structure is never written to, we can statically allocate
it to avoid the stack usage.

Fixes: 7445cfb1 ("net/mlx5: E-Switch, Tag packet with vport number in VF vports and uplink ingress ACLs")
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Reviewed-by: Jianbo Liu <jianbol@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>