net: phy: add callback for custom interrupt handler to struct phy_driver

The phylib interrupt handler handles link change events only currently.
However PHY drivers may want to use other interrupt sources too,
e.g. to report temperature monitoring events. Therefore add a callback
to struct phy_driver allowing PHY drivers to implement a custom
interrupt handler.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Suggested-by: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>