[RESEND PATCH v1 2/4] net: ethernet: arc: Keep emac compatibility for more Rockchip SoCs

On the RK3066/RK3188, there was fixed GRF offset configuration to set emac and fixed DIV2 mac TX/RX clock. So, we need to easily set and fit to other SoCs (RK3036) which maybe have different GRF offset, and need adjust mac TX/RX clock. Signed-off-by: Xing Zheng ---

[RESEND PATCH v1 2/4] net: ethernet: arc: Keep emac compatibility for more Rockchip SoCs

On the RK3066/RK3188, there was fixed GRF offset configuration to set emac and fixed DIV2 mac TX/RX clock. So, we need to easily set and fit to other SoCs (RK3036) which maybe have different GRF offset, and need adjust mac TX/RX clock. Signed-off-by: Xing Zheng ---