regulator: dt-bindings: Add Allwinner D1 system LDOs

The Allwinner D1 SoC contains two pairs of in-package LDOs. The pair of
"system" LDOs is for general purpose use. LDOA generally powers the
board's 1.8 V rail. LDOB powers the in-package DRAM, where applicable.
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Link: https://lore.kernel.org/r/20240509153107.438220-2-wens@kernel.orgSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/allwinner,sun20i-d1-system-ldos.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/regulator/allwinner,sun20i-d1-system-ldos.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Allwinner D1 System LDOs
+
+maintainers:
+  - Samuel Holland <samuel@sholland.org>
+
+description:
+  Allwinner D1 contains a pair of general-purpose LDOs which are designed to
+  supply power inside and outside the SoC. They are controlled by a register
+  within the system control MMIO space.
+
+properties:
+  compatible:
+    enum:
+      - allwinner,sun20i-d1-system-ldos
+
+  reg:
+    maxItems: 1
+
+patternProperties:
+  "^ldo[ab]$":
+    type: object
+    $ref: regulator.yaml#
+    unevaluatedProperties: false
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+...