ARM: dts: stm32: Add DAC support to stm32mp157c-ed1

stm32mp157c-ed1 board has digital-to-analog converter signals routed
to JP11 and JP10 jumpers (e.g. PA4/PA5).
It's easier then to configure them both. But keep them disabled by default,
so the pins are kept in their initial state to lower power consumption.
This way they can also be used as GPIO.

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