net: dsa: mv88e6xxx: Add 6352 family PCS registers to ethtool -d

The mv88e6352 has one PCS which can be used for 1000BaseX or
SGMII. Add the registers to the dump for the port which the PCS is
associated to.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>