net/mlx5: Allocate smaller size tables for ft offload

Instead of giving ft tables one of the largest tables available - 4M,
give it a more reasonable size - 64k. Especially since it will
always be created as a miss hook in the following patch.

Signed-off-by: Paul Blakey <paulb@mellanox.com>
Reviewed-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>