ARM: dts: stm32: add ADC pins used on stm32mp157a-dk1

Define pins that can be used for ADC on stm32mp157a-dk1 board:
- AIN connector has ADC input pins
- USB Type-C CC1 & CC2 pins (e.g. in18, in19)

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>