dt-bindings: bus: fsl,imx8qxp-pixel-link-msi-bus: Drop child 'reg' property

A bus schema based on simple-pm-bus shouldn't define how many 'reg' entries
a child device has. That is a property of the device. Drop the 'reg' entry.

Reviewed-by: Liu Ying <victor.liu@nxp.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230925212639.1975002-1-robh@kernel.org


Signed-off-by: Rob Herring <robh@kernel.org>