dt-bindings: remove 'interrupt-parent' from bindings

'interrupt-parent' is often documented as part of define bindings, but
it is really outside the scope of a device binding. It's never required
in a given node as it is often inherited from a parent node. Or it can
be implicit if a parent node is an 'interrupt-controller' node. So
remove it from all the binding files.

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: devicetree@vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/cpufreq/brcm,stb-avs-cpu-freq.txt

@@ -29,8 +29,6 @@ Required properties:
 - reg: Specifies base physical address and size of the registers.
 - interrupts: The interrupt that the AVS CPU will use to interrupt the host
               when a command completed.
-- interrupt-parent: The interrupt controller the above interrupt is routed
-                    through.
 - interrupt-names: The name of the interrupt used to interrupt the host.
 
 Optional properties: