dt-bindings: Move altr,msi-controller to interrupt-controller directory
While altr,msi-controller is used with PCI, it is not a PCI host bridge
and is just an MSI provider. Move it with other MSI providers in the
'interrupt-controller' directory.
Acked-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20250507154253.1593870-1-robh@kernel.org
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>