stm32mp: fix compilation issue with DEBUG_UART

Fix the compilation issue when CONFIG_DEBUG_UART is activated

drivers/serial/serial_stm32.o: in function `debug_uart_init':
drivers/serial/serial_stm32.c:291: undefined reference to \
`board_debug_uart_init'

The board_debug_uart_init is needed for SPL boot, called in
cpu.c::mach_cpu_init(); it is defined in board/st/stm32mp1/spl.c.

But with the removal #ifdefs patch, the function debug_uart_init() is
always compiled even if not present in the final U-Boot image.

This patch adds a file to provided this function when DEBUG_UART and SPL
are activated.

Fixes: c8b2eef52b6c ("stm32mp15: tidy up #ifdefs in cpu.c")
Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>

board: stm32: Add Engicam i.Core STM32MP1 EDIMM2.2 Starter Kit

Engicam EDIMM2.2 Starter Kit is an EDIMM 2.2 Form Factor Capacitive
Evaluation Board.

Genaral features:
- LCD 7" C.Touch
- microSD slot
- Ethernet 1Gb
- Wifi/BT
- 2x LVDS Full HD interfaces
- 3x USB 2.0
- 1x USB 3.0
- HDMI Out
- Mini PCIe
- MIPI CSI
- 2x CAN
- Audio Out

i.Core STM32MP1 is an EDIMM SoM based on STM32MP157A from Engicam.

i.Core STM32MP1 needs to mount on top of this Evaluation board for
creating complete i.Core STM32MP1 EDIMM2.2 Starter Kit.

Linux dts commit details:

commit <adc0496104b6> ("ARM: dts: stm32: Add Engicam i.Core STM32MP1
EDIMM2.2 Starter Kit")

Add support for it.

Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>

board: stm32: Add Engicam i.Core STM32MP1 EDIMM2.2 Starter Kit

Engicam EDIMM2.2 Starter Kit is an EDIMM 2.2 Form Factor Capacitive
Evaluation Board.

Genaral features:
- LCD 7" C.Touch
- microSD slot
- Ethernet 1Gb
- Wifi/BT
- 2x LVDS Full HD interfaces
- 3x USB 2.0
- 1x USB 3.0
- HDMI Out
- Mini PCIe
- MIPI CSI
- 2x CAN
- Audio Out

i.Core STM32MP1 is an EDIMM SoM based on STM32MP157A from Engicam.

i.Core STM32MP1 needs to mount on top of this Evaluation board for
creating complete i.Core STM32MP1 EDIMM2.2 Starter Kit.

Linux dts commit details:

commit <adc0496104b6> ("ARM: dts: stm32: Add Engicam i.Core STM32MP1
EDIMM2.2 Starter Kit")

Add support for it.

Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>