Remove several warnings reported with W=1

Improved support for W=1 compilation flag by solving missing-prototypes
and old-style-definition warnings.

The libraries are compiling with warnings (which turn into errors with
the Werror flag).

Outside of libraries, some warnings cannot be fixed without heavy
structural changes.

Change-Id: I1668cf99123ac4195c2a6a1d48945f7a64c67f16
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>
diff --git a/include/plat/arm/common/plat_arm.h b/include/plat/arm/common/plat_arm.h
index 9d6786f..527375f 100644
--- a/include/plat/arm/common/plat_arm.h
+++ b/include/plat/arm/common/plat_arm.h
@@ -187,6 +187,7 @@
 void arm_bl2_plat_arch_setup(void);
 uint32_t arm_get_spsr_for_bl32_entry(void);
 uint32_t arm_get_spsr_for_bl33_entry(void);
+int arm_bl2_plat_handle_post_image_load(unsigned int image_id);
 int arm_bl2_handle_post_image_load(unsigned int image_id);
 struct bl_params *arm_get_next_bl_params(void);