On STM32MP1 EVAL and DISCOVERY boards, the SDMMC3 internal peripheral
can be used through the GPIO extension connector. The sdmmc3 node is then
added in the boards DT files, and the required pins are also added.
The node status is disabled as there is no device connected by default.
Signed-off-by: Ludovic Barre <ludovic.barre@st.com>
Signed-off-by: Yann Gautier <yann.gautier@st.com>