feat(plat/st): add STM32CubeProgrammer support on UART

Add a file to support the STMicroelectronics tool STM32CubeProgrammer
over UART in BL2 for STM32MP15x platform.

This tools is based on protocol defined in AN5275,
"USB DFU/USART protocols used in STM32MP1 Series bootloaders"
based on STM32 MCU protocols (AN3155, "USART protocol used
in the STM32 bootloader").

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Change-Id: I956c95d8de0a94d1eb8e61f043651dae7b838170
diff --git a/plat/st/common/include/stm32cubeprogrammer.h b/plat/st/common/include/stm32cubeprogrammer.h
index 503d919..0f5a64d 100644
--- a/plat/st/common/include/stm32cubeprogrammer.h
+++ b/plat/st/common/include/stm32cubeprogrammer.h
@@ -24,4 +24,6 @@
 			   uintptr_t ssbl_base,
 			   size_t ssbl_len);
 
+int stm32cubeprog_uart_load(uintptr_t instance, uintptr_t base, size_t len);
+
 #endif /* STM32CUBEPROGRAMMER_H */