ARM: dts: stm32: Add alternate pinmux for SDMMC1 direction pins

Add another mux option for SDMMC1 direction pins, in particular
SDMMC1_D123DIR, this is used on AV96 board.

Reviewed-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@st.com>
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: Patrick Delaunay <patrick.delaunay@st.com>
Cc: Patrice Chotard <patrice.chotard@st.com>