stmmac: dwmac-socfpga: call phy_resume() only in resume callback

Calling phy_resume() should only be need during driver resume to
workaround a hardware errata.

Signed-off-by: Joachim Eastwood <manabian@gmail.com>
Tested-by: Marek Vasut <marex@denx.de>
Signed-off-by: David S. Miller <davem@davemloft.net>