net: phy: restore mdio regs in the iproc mdio driver

net: phy: restore mdio regs in the iproc mdio driver

commit 3c0338835167c28241a280bf741027ef90583099 upstream.

The mii management register in iproc mdio block
does not have a retention register so it is lost on suspend.
Save and restore value of register while resuming from suspend.

Fixes: 468f1a0bebf0 ("net: phy: Initialize mdio clock at probe function")
Signed-off-by: Arun Parameswaran <arun.parameswaran@broadcom.com>
Signed-off-by: Scott Branden <scott.branden@broadcom.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>