dt-bindings: power: apple,pmgr-pwrstate: Add t6020 compatible

dt-bindings: power: apple,pmgr-pwrstate: Add t6020 compatible

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

The implementation on Apple M2 Pro/Max/Ultra SoCs is compatible so add
its per-SoC compatible with the new base.

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

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