net: phy: micrel: enable interrupt for ksz9477 phy

Config_intr and handle_interrupt are enabled for ksz9477 phy. It is
similar to all other phys in the micrel phys.

Signed-off-by: Arun Ramadoss <arun.ramadoss@microchip.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>