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/stm32mp1/bl2_plat_setup.c b/plat/st/stm32mp1/bl2_plat_setup.c
index 1504360..33ad56f 100644
--- a/plat/st/stm32mp1/bl2_plat_setup.c
+++ b/plat/st/stm32mp1/bl2_plat_setup.c
@@ -139,6 +139,8 @@
 				  u_register_t arg2 __unused,
 				  u_register_t arg3 __unused)
 {
+	stm32mp_setup_early_console();
+
 	stm32mp_save_boot_ctx_address(arg0);
 }