linux-imx

regulator: Add STM32 Voltage Reference Buffer

Document STM32 VREFBUF (voltage reference buffer) which can be used as
voltage reference for ADCs, DACs and external components.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>