net: phy: marvell: Avoid unnecessary soft reset

The BMCR.RESET bit on the Marvell PHYs has a special meaning in that
it commits the register writes into the HW for it to latch and be
configured appropriately. Doing software resets causes link drops, and
this is unnecessary disruption if nothing changed.

Determine from marvell_set_polarity()'s return code whether the register value
was changed and if it was, propagate that to the logic that hits the software
reset bit.

This avoids doing unnecessary soft reset if the PHY is configured in
the same state it was previously, this also eliminates the need for a
m88e1111_config_aneg() function since it now is the same as
marvell_config_aneg().

Tested-by: Wang, Dongsheng <dongsheng.wang@hxt-semitech.com>
Tested-by: Chris Healy <cphealy@gmail.com>
Tested-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Clemens Gruber <clemens.gruber@pqgruber.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>