SST: Add rollback protection in SST service

This patch adds rollback protection in SST service, enables it for all
supported platforms and updates the SST service integration guide.

Change-Id: If4697051824766e1ae5774ede0e9960088bdd46a
Signed-off-by: Marc Moreno <marc.morenoberengue@arm.com>
diff --git a/CommonConfig.cmake b/CommonConfig.cmake
index af7af02..77ba88e 100644
--- a/CommonConfig.cmake
+++ b/CommonConfig.cmake
@@ -193,6 +193,10 @@
 		set (SST_ENCRYPTION ON)
 	endif()
 
+	if (NOT DEFINED SST_ROLLBACK_PROTECTION)
+		set (SST_ROLLBACK_PROTECTION OFF)
+	endif()
+
 	if (NOT DEFINED SST_CREATE_FLASH_LAYOUT)
 		set (SST_CREATE_FLASH_LAYOUT OFF)
 	endif()