dt-bindings: soc: microchip: use absolute path to other schema

Absolute path to other DT schema is preferred over relative one.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220726115841.101249-4-krzysztof.kozlowski@linaro.org