dt-bindings: arm: apple: apple,pmgr: Add t6020-pmgr compatible

dt-bindings: arm: apple: apple,pmgr: Add t6020-pmgr compatible

After discussion with the devicetree maintainers we agreed to not extend
lists with the generic compatible "apple,pmgr" anymore [1]. Use
"apple,t8103-pmgr" as base compatible as it is the SoC the bindings were
written for.

The block on Apple M2 Pro/Max/Ultra SoCs is compatible with
"apple,t8103-pmgr" so use it as fallback compatible and add t6020 as
per-SoC compatible.

[1]: https://lore.kernel.org/asahi/12ab93b7-1fc2-4ce0-926e-c8141cfe81bf@kernel.org/

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Neal Gompa <neal@gompa.dev>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Janne Grunau <j@jannau.net>