bl1: include bl1_private.h in aarch* files

This change avoids warnings when setting -Wmissing-prototypes or when
using sparse tool.

Signed-off-by: Yann Gautier <yann.gautier@st.com>
Signed-off-by: Etienne Carriere <etienne.carriere@st.com>
diff --git a/bl1/aarch32/bl1_arch_setup.c b/bl1/aarch32/bl1_arch_setup.c
index 23a6564..ce04aaa 100644
--- a/bl1/aarch32/bl1_arch_setup.c
+++ b/bl1/aarch32/bl1_arch_setup.c
@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
+#include "../bl1_private.h"
 
 /*******************************************************************************
  * TODO: Function that does the first bit of architectural setup.