ARM: l2c: imx vf610: convert to generic l2c OF initialisation

Remove the explicit call to l2x0_of_init(), converting to the generic
infrastructure instead.  Since the .init_irq method only calls
irqchip_init(), we can remove that too as the generic code will take
care of that.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>