net: ethernet: stmmac: dwmac-rk: Add RK3328 gmac support

Add constants and callback functions for the dwmac on rk3328 socs.
As can be seen, the base structure is the same, only registers and the
bits in them moved slightly.

Signed-off-by: david.wu <david.wu@rock-chips.com>
Signed-off-by: David S. Miller <davem@davemloft.net>