emulation: qemu-sbsa: Move ITS node into GICv3 node

According to the binding [1] the ITS node should be a subnode of the
GICv3 node. Thus move it now that the driver binds subnodes as well.

1: https://www.kernel.org/doc/Documentation/devicetree/bindings/interrupt-controller/arm%2Cgic-v3.txt

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
2 files changed