Update the sdmmc2 node for eMMC support on eval board stm32mp157c-ev1. - update slew-rate for pin configuration - update "vqmmc-supply" - remove "st,sig-dir" - add mandatory "pinctrl-names" - add "mmc-ddr-3_3v" This patch solve the eMMC detection issue for command "mmc dev 1". Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>