irqdomain: Convert irqdomain-%3Eof_node to fwnode

irqdomain: Convert irqdomain-%3Eof_node to fwnode

Now that we have everyone accessing the of_node field via the
irq_domain_get_of_node accessor, it is pretty easy to swap it
for a pointer to a fwnode_handle.

This translates into a few limited changes in __irq_domain_add,
and an updated irq_domain_get_of_node.

Signed-off-by: Marc Zyngier <[email protected]>
Reviewed-and-tested-by: Hanjun Guo <[email protected]>
Tested-by: Lorenzo Pieralisi <[email protected]>
Cc: <[email protected]>
Cc: Tomasz Nowicki <[email protected]>
Cc: Suravee Suthikulpanit <[email protected]>
Cc: Graeme Gregory <[email protected]>
Cc: Jake Oshins <[email protected]>
Cc: Jiang Liu <[email protected]>
Cc: Jason Cooper <[email protected]>
Cc: Rafael J. Wysocki <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>