dt-bindings: mfd: qcom,spmi-pmic: Extend example

Add a more complete example with PM6150 to provide better validation of
the bindings.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20220828130113.5845-1-krzysztof.kozlowski@linaro.org