dt-bindings: intel,ixp4xx-expansion-bus: split out peripheral properties

The properties of devices in IXP4xx expansion bus need to be also
applied to actual devices' bindings.  Prepare for this by splitting them
to separate intel,ixp4xx-expansion-peripheral-props binding, just like
other memory-controller peripheral properties.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20230206092624.22922-2-krzysztof.kozlowski@linaro.org


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