net/mlx4: Move Ethernet related functionality from mlx4_core to mlx4_en

Move low level code that deals with management of Ethernet MACs and QPs from mlx4_core to mlx4_en.
Also convert the new functions to deal with MACs in form of char array instead of u64.

Actual functions moved:
mlx4_replace_mac
mlx4_get_eth_qp
mlx4_put_eth_qp

To conduct this change, some functionality had to be exported from the core,
the following functions were added:
mlx4_get_base_qp
__mlx4_replace_mac (low level function for CX1/A0 compatibility)

Signed-off-by: Yan Burman <yanb@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>