e6000sw's probe was doing far too much: it walked OF_finddevice("/")
looking for a "marvell,mv88e6085" or "marvell,mv88e6190" node
anywhere in the tree, filled in most of the softc, spun up a
throwaway sx lock just to read SWITCH_ID over MDIO,
port-count / phy-base from the ID. Any board with FDT enabled ran
all of that whether or not it had a Marvell switch on a given MDIO
device.

Split the work along the usual newbus boundary:

• Make e6000sw_probe() the trivial probe that it should be, moving the meat into e600sw_attach() where it belongs.

• e6000sw_attach() updates the description after it determines the device in setup.

• e6000sw_identify() skips FDT parents; on hint-only builds it still adds the wildcard child as before.