dt-bindings: PCI: dwc: Remove bus node from the examples

It's absolutely redundant seeing by default each node is embedded into its
own example-X node with address and size cells set to 1.

Link: https://lore.kernel.org/r/20221113191301.5526-5-Sergey.Semin@baikalelectronics.ru


Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>