feat(st): add early console in BL2

Add an early UART console to ease debug before UART is fully configured.
This is done under flag STM32MP_EARLY_CONSOLE in the first STM32MP1
platform function called (bl2_el3_early_platform_setup()). It uses the
parameters defined for crash console: STM32MP_DEBUG_USART* macros.

Signed-off-by: Yann Gautier <yann.gautier@st.com>
Change-Id: Id6be62368723a0499e97bbf56fb52c166fcbdfad
diff --git a/plat/st/common/include/stm32mp_common.h b/plat/st/common/include/stm32mp_common.h
index a13e9e5..d8d1c13 100644
--- a/plat/st/common/include/stm32mp_common.h
+++ b/plat/st/common/include/stm32mp_common.h
@@ -62,6 +62,14 @@
 /* Setup the UART console */
 int stm32mp_uart_console_setup(void);
 
+#if STM32MP_EARLY_CONSOLE
+void stm32mp_setup_early_console(void);
+#else
+static inline void stm32mp_setup_early_console(void)
+{
+}
+#endif
+
 /*
  * Platform util functions for the GPIO driver
  * @bank: Target GPIO bank ID as per DT bindings