regulator: dt-bindings: document the SGM3804 Dual Output regulator

regulator: dt-bindings: document the SGM3804 Dual Output regulator

Document the SG Micro SGM3804 Single Inductor Dual Output Buck/Boost
Converter used to power LCD panels a provide positive and negative
power rails with configurable voltage and active discharge function
for each output.

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patch.msgid.link/20260522-topic-sm8650-ayaneo-pocket-s2-sgm3804-v5-1-bd6b1c300ecc@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>