stmmac: dwmac-rk: use rk_gmac_ops as of match data

Remove the setup glue callback and use rk_gmac_ops as OF match
data so it can used directly when calling rk_gmac_setup.

Signed-off-by: Joachim Eastwood <manabian@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>