Add platform hooks for boot redundancy support

These hooks are intended to allow one platform to try load
images from alternative places. There is a hook to initialize
the sequence of boot locations and a hook to pass to the next
sequence.

Change-Id: Ia0f84c415208dc4fa4f9d060d58476db23efa5b2
Signed-off-by: Roberto Vargas <roberto.vargas@arm.com>
diff --git a/include/plat/common/platform.h b/include/plat/common/platform.h
index f03a399..e2bfa50 100644
--- a/include/plat/common/platform.h
+++ b/include/plat/common/platform.h
@@ -100,6 +100,8 @@
 void plat_error_handler(int err) __dead2;
 void plat_panic_handler(void) __dead2;
 const char *plat_log_get_prefix(unsigned int log_level);
+void bl2_plat_preload_setup(void);
+int plat_try_next_boot_source(void);
 
 /*******************************************************************************
  * Mandatory BL1 functions