Add support for SSC_VERSION register on CSS platforms

Each ARM Compute Subsystem based platform implements a System Security
Control (SSC) Registers Unit. The SSC_VERSION register inside it carries
information to identify the platform. This enables ARM Trusted Firmware
to compile in support for multiple ARM platforms and choose one at
runtime. This patch adds macros to enable access to this register.
Each platform is expected to export its PART_NUMBER separately.

Additionally, it also adds juno part number.

Change-Id: I2b1d5f5b65a9c7b76c6f64480cc7cf0aef019422
diff --git a/plat/arm/board/juno/juno_def.h b/plat/arm/board/juno/juno_def.h
index 1f367f2..f4e2259 100644
--- a/plat/arm/board/juno/juno_def.h
+++ b/plat/arm/board/juno/juno_def.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014-2015, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2014-2016, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -50,6 +50,7 @@
 #define PSRAM_BASE			0x14000000
 #define PSRAM_SIZE			0x02000000
 
+#define JUNO_SSC_VER_PART_NUM		0x030
 
 /*******************************************************************************
  * TZC-400 related constants