dt-bindings: arm: qcom: Document xiaomi,laurel-sprout board

Document the Xiaomi Mi A3 (xiaomi-laurel-sprout) smartphone which is
based on the Snapdragon 665 SoC.

Signed-off-by: Lux Aliaga <they@mint.lgbt>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230306170817.3806-6-they@mint.lgbt