arm: vf610: zii devel b: Add support for switch interrupts

The Switches use GPIO lines to indicate interrupts from two of the
switches.

With these interrupts in place, we can make use of the interrupt
controllers within the switch to indicate when the internal PHYs
generate an interrupt. Use standard PHY properties to do this.

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