dt-bindings: mfd: x-powers,axp152: Document the AXP15060 variant

dt-bindings: mfd: x-powers,axp152: Document the AXP15060 variant

The X-Powers AXP15060 is a PMIC seen on Starfive Visionfive 2 board. Add
relative compatible item and CPUSLDO support and disables DC-DC
frequency setting for it.

Signed-off-by: Shengyu Qu <wiagn233@outlook.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
[Backported patch : https://lore.kernel.org/lkml/TY3P286MB261177CF7AA2959BD9517DA998609@TY3P286MB2611.JPNP286.PROD.OUTLOOK.COM/]
Signed-off-by: Hoegeun Kwon <hoegeun.kwon@samsung.com>
Change-Id: Ia8ada01c0f0e56642a14401d34a1b2a47ddf6851