net: stmmac: dwmac-rk: fixes the gmac resume after PD on/off

GMAC Power Domain(PD) will be disabled during suspend.
That will causes GRF registers reset.
So corresponding GRF registers for GMAC must be setup again.

Signed-off-by: Roger Chen <roger.chen@rock-chips.com>
Signed-off-by: Caesar Wang <wxt@rock-chips.com>
Signed-off-by: David S. Miller <davem@davemloft.net>