Add a specific command stm32prog for STM32MP soc family
witch allows to program the boot devices with the tool
STM32CubeProgrammer (http://www.st.com/STM32CubeProg).

This command uses the same UART STM32 protocol than MCU
STM32 with or USB with DFU protocol v1.1 (ithe MCU ST
extension are no supported).

The executed actions are based on a tab separated value file
with a stm32 header, the FlashLayout file
(https://wiki.st.com/stm32mpu/wiki/STM32CubeProgrammer_flashlayout).

This file is parsed by the U-Boot command to:
- initialize the devices
- create the partition table on each device
- initialize the DFU backend to access to not volatile memory
  (NOR/NAND/SD/eMMC) or to virtual device (OTP/PMIC)

Up to STM32PROG_MAX_DEV (5) devices can be updated with a FlashLayout.

The communication between U-Boot and STM32CubeProgrammer is done with
the specific alternate configuration (see "AN5275: USB DFU/USART protocols
used in STM32MP1 Series bootloaders" for details).

The command stm32prog is executed when a boot from USB is detected
(selected with bootpins) and we can program the boot devices with
a simple command (on Windows or Linux):

PC $>  STM32_Programmer_CLI -c port=usb1 -w flaslayout.tsv

1/ the ROM code loads TF-A in embedded RAM (DFU or uart)
2/ TF-A loads flashlayout file and U-Boot in DDR (DFU or uart)
3/ U-Boot executes the stm32prog command (DFU or uart)
Signed-off-by: NPatrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: NPatrice Chotard <patrice.chotard@st.com>
Reviewed-by: NPatrice Chotard <patrice.chotard@st.com>