correct some missing-prototype warnings

This avoids the following warnings:
no previous prototype for 'bl2_arch_setup' [-Wmissing-prototypes]
no previous prototype for 'plat_log_get_prefix' [-Wmissing-prototypes]

Also correct a compilation issue if BL2_IN_XIP_MEM is enabled:
uintptr_t is not defined.

Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Signed-off-by: Yann Gautier <yann.gautier@st.com>
diff --git a/bl2/aarch32/bl2_arch_setup.c b/bl2/aarch32/bl2_arch_setup.c
index db8a068..4fd8d07 100644
--- a/bl2/aarch32/bl2_arch_setup.c
+++ b/bl2/aarch32/bl2_arch_setup.c
@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
+#include "../bl2_private.h"
 
 /*******************************************************************************
  * Place holder function to perform any Secure SVC specific architectural