mlx4_core: Move DMFS HW structs to common header file

Move flow steering HW structures to be on the public mlx4 include
directory, as a pre-step for the mlx4 IB driver to use them too.

Signed-off-by: Hadar Hen Zion <hadarh@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>