ARM: dts: stm32mp: factor out common DK nodes into dtsi ...

The DK2 appears to be just the DK1 with a display, thus factor out the
barebox-specifics into a new stm32mp157a-dk1.dtsi, which we can include
in both device trees after including the upstream device tree.

As the updated device tree introduced new nodes, the now duplicates
(&ethernet0, &uart4, /chosen and /aliases) are dropped from the barebox
device as part of this commit as well.

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

ARM: dts: stm32mp157a-dk1.dts: include upstream dts before barebox' ...

To allow "stm32mp157c.dtsi" to extend nodes in <arm/stm32mp157c.dtsi>,
it should be included after it. Do this.

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

ARM: Add initial STM32MP1 support ...

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>