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.org
Signed-off-by: Mark Brown <broonie@kernel.org>