UPSTREAM: net: ethernet: arc: Probe emac after set RMII clock

UPSTREAM: net: ethernet: arc: Probe emac after set RMII clock

After enter arc_emac_probe, emac will get_phy_id, phy_poll_reset and
other connecting PHY via mdiobus_read, so we need to set correct
ref clock rate for emac before probe emac.

Change-Id: Iffaa7a60efcfcadded803df7c0b20e5a2422d646
Signed-off-by: Xing Zheng <zhengxing@rock-chips.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Caesar Wang <wxt@rock-chips.com>
(cherry picked from commit c9bca2fe3ca6d6dac2a27eb8619955648369efed)