net: dsa: mv88e6xxx: Add MDIO interrupts for internal PHYs

When registering an MDIO bus, it is possible to pass an array of
interrupts, one per address on the bus. phylib will then associate the
interrupt to the PHY device, if no other interrupt is provided.

Some of the global2 interrupts are PHY interrupts. Place them into the
MDIO bus structure.

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