regmap-irq: use fwnode instead of device node in add_irq_chip()

Convert the argument to the newer fwnode_handle instead a device tree
node. Fortunately, there are no users for now. So this is an easy
change.

Signed-off-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20200706175353.16404-2-michael@walle.cc


Signed-off-by: Mark Brown <broonie@kernel.org>