Add support for STM32MP1 ADC. It's quite similar to STM32H7 ADC.
Introduce new compatible to handle variants of this hardware such as
vregready flag, trigger list, interrupts, clock rate.
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>