dt-bindings: xlnx,vcu-settings: fix dt_binding_check warnings

dt-bindings: xlnx,vcu-settings: fix dt_binding_check warnings

When running make dt_binding_check, the xlnx,vcu-settings binding
triggers the following two warnings:

	'additionalProperties' is a required property

	example-0: vcu@a0041000:reg:0: [0, 2684620800, 0, 4096] is too long

Fix the binding and make the checker happy.

Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201202090522.251607-1-m.tretter@pengutronix.de
Signed-off-by: Rob Herring <robh@kernel.org>