ARM: dts: stm32: Reinstate SPL_SYS_MMCSD_RAW_MODE on DH STM32MP15xx DHSOM

ARM: dts: stm32: Reinstate SPL_SYS_MMCSD_RAW_MODE on DH STM32MP15xx DHSOM

Commit 2a00d73d081a ("spl: mmc: Try to clean up raw-mode options")
broke booting from SD card on STM32MP15xx , reinstate raw mode SD
boot configuration options and select the correct raw mode partition
for STM32MP15xx to fix SD boot on STM32MP15xx DHSOM.

Fixes: 2a00d73d081a ("spl: mmc: Try to clean up raw-mode options")
Reported-by: Patrice Chotard <patrice.chotard@foss.st.com>
Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>