dt-bindings: PCI: fsl,layerscape-pcie-ep: Drop deprecated windows

The example DTS uses 'num-ib-windows' and 'num-ob-windows' properties
but these are not defined in the binding. Binding also does not
reference snps,dw-pcie-common.yaml, probably because it is quite
different even though the device is based on Synopsys controller.

The properties are actually deprecated, so simply drop them from the
example.

Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Krzysztof Wilczyński <[e-mail]>
Reviewed-by: Frank Li <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/devicetree/bindings/pci/fsl,layerscape-pcie-ep.yaml

···
         reg-names = "regs", "addr_space";
         interrupts = <GIC_SPI 108 IRQ_TYPE_LEVEL_HIGH>; /* PME interrupt */
         interrupt-names = "pme";
-        num-ib-windows = <6>;
-        num-ob-windows = <8>;
         status = "disabled";
       };
     };