There's new infrastructure for runtime determining RAM size. Use it so
we don't need to hard code it in PBL and board code.

Because this new infrastructure has some nested function calls, my
arm-v7a-linux-gnueabihf-gcc 9.2.1 (OSELAS.Toolchain-2019.09.0)
spills to the stack.  Add stm32mp_cpu_lowlevel_init, which also sets up
a stack after barebox end so this works.

Lastly, there's no upstream device tree node for the DDR controller.
Add one in the barebox device tree, so we don't have to hardcode the
DDRCTRL address into non-pbl code that's run everywhere.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Now with the SD/MMC controller supported, lets add a bbu handler, so we
can use it to update the second stage boot loader partition.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

dk2_postcore_init is not at postcore init level like the name would
suggest, but at mem init level. Rename it accordingly.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

This adds initial STMicroelectronics MP1 support along with support
for the DK2 devel board. Only very basic support:

- UART
- SDRAM memory base/size
- No 1st stage support

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>