net: phy: at803x: make read specific status function more generic

Rework read specific status function to be more generic. The function
apply different speed mask based on the PHY ID. Make it more generic by
adding an additional arg to pass the specific speed (ss) mask and use
the provided mask to parse the speed value.

This is needed to permit an easier deatch of qca808x code from the
at803x driver.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>