Add support for BL3-1 as a reset vector

This change adds optional reset vector support to BL3-1
which means BL3-1 entry point can detect cold/warm boot,
initialise primary cpu, set up cci and mail box.

When using BL3-1 as a reset vector it is assumed that
the BL3-1 platform code can determine the location of
the BL3-2 images, or load them as there are no parameters
that can be passed to BL3-1 at reset.

It also fixes the incorrect initialisation of mailbox
registers on the FVP platform

This feature can be enabled by building the code with
make variable RESET_TO_BL31 set as 1

Fixes ARM-software/TF-issues#133
Fixes ARM-software/TF-issues#20

Change-Id: I4e23939b1c518614b899f549f1e8d412538ee570
diff --git a/bl31/bl31.mk b/bl31/bl31.mk
index c0dc2fd..6c9650f 100644
--- a/bl31/bl31.mk
+++ b/bl31/bl31.mk
@@ -37,6 +37,7 @@
 				bl31/aarch64/runtime_exceptions.S		\
 				bl31/aarch64/crash_reporting.S	\
 				common/aarch64/early_exceptions.S		\
+				lib/aarch64/cpu_helpers.S			\
 				lib/locks/bakery/bakery_lock.c			\
 				lib/locks/exclusive/spinlock.S			\
 				services/std_svc/std_svc_setup.c		\