mlx4: In RoCE allow guests to have multiple GIDS

The GIDs are statically distributed, as follows:
PF: gets 16 GIDs
VFs:  Remaining GIDS are divided evenly between VFs activated by the driver.
      If the division is not even, lower-numbered VFs get an extra GID.

For an IB interface, the number of gids per guest remains as before: one gid per guest.

Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>