stm32mp: stm32prog: change default flashlayout location to CONFIG_SYS_LOAD_ADDR

stm32mp: stm32prog: change default flashlayout location to CONFIG_SYS_LOAD_ADDR

Change the defaut flashlayout location, hardcoded at STM32_DDR_BASE,
to CONFIG_SYS_LOAD_ADDR to avoid issue on board with reserved memory
at STM32_DDR_BASE.

This patch changes the command behavior for STM32MP13 and STM32MP15
platform, as CONFIG_SYS_LOAD_ADDR(0xc2000000) != STM32_DDR_BASE
but without impact for serial boot with STM32CubeProgrammer.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>