net: stmmac: dwmac-rk: Add integrated PHY supprot for rk3328

There are two mac controllers in the rk3328, the one connects
to external PHY, and the other one connects to integrated PHY.
Like the mac of external PHY, the integrated PHY's mac also
needs to configure the related mac registers at GRF.

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