net/mlx4_core: Put Firmware flow steering structures in common header files

To allow for usage of the flow steering Firmware structures in more locations over the driver,
such as the resource tracker, move them from mcg.c to common header files.

Signed-off-by: Hadar Hen Zion <hadarh@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>