dsa: Add reporting of silicon revision for Marvell 88E6123/88E6161/88E6165 switches.

Add reporting of silicon revision during the probe function for Marvell 88E6123/88E6161/88E6165 switches.

Signed-off-by: Chris Healy <cphealy@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>