refactor(stm32mp1): move stm32_save_boot_interface()

The function stm32_save_boot_interface()is moved to stm32mp1_private.c
file. The files stm32mp1_context.{c,h} are removed.
As return is always 0, change the function to return void.
Call it earlier, to be able to use it when configuring console.

Change-Id: I8986e1257dc8e8708eab044a51ea1f2426b16597
Signed-off-by: Yann Gautier <yann.gautier@foss.st.com>
diff --git a/plat/st/common/include/stm32mp_common.h b/plat/st/common/include/stm32mp_common.h
index 693640f..5eac5cc 100644
--- a/plat/st/common/include/stm32mp_common.h
+++ b/plat/st/common/include/stm32mp_common.h
@@ -115,4 +115,7 @@
 int stm32mp_map_ddr_non_cacheable(void);
 int stm32mp_unmap_ddr(void);
 
+/* Function to save boot peripheral info */
+void stm32_save_boot_interface(uint32_t interface, uint32_t instance);
+
 #endif /* STM32MP_COMMON_H */