cbus: tahvo: give it an irq_chip

tahvo also has IRQs to demux to its children,
so lets give it a struct irq_chip so that child
drivers can use standard request_threaded_irq().

This is still an unused irq_chip, later patches
will come to make proper use of it.

Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

diff --cc drivers/cbus/tahvo.c
Simple merge