Document qcom,pmc8180 and qcom,pmc8180c compatibles already used in DTS:

  sc8180x-primus.dtb: pmic@1: compatible:0: 'qcom,pmc8180' is not one of ...
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230720083525.73622-1-krzysztof.kozlowski@linaro.orgSigned-off-by: Lee Jones <lee@kernel.org>