net: dsa: sja1105: apply RGMII delays based on the fixed-link property

The sja1105 driver has an intermediate way of determining whether the
RGMII delays should be applied by the PHY or by itself: by looking at
the port role (PHY or MAC). The port can be put in the PHY role either
explicitly (sja1105,role-phy) or implicitly (fixed-link).

We want to deprecate the sja1105,role-phy property, so all that remains
is the fixed-link property. Introduce a "fixed_link" array of booleans
in the driver, and use that to determine whether RGMII delays must be
applied or not.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>