Move CPU context pointers into cpu_data

Moving the context pointers for each CPU into the per-cpu data
allows for much more efficient access to the contexts for the
current CPU.

Change-Id: Id784e210d63cbdcddb44ac1591617ce668dbc29f
diff --git a/include/bl31/context.h b/include/bl31/context.h
index b889f68..c0230b8 100644
--- a/include/bl31/context.h
+++ b/include/bl31/context.h
@@ -188,6 +188,7 @@
 #ifndef __ASSEMBLY__
 
 #include <cassert.h>
+#include <platform_def.h>	/* for CACHE_WRITEBACK_GRANULE */
 #include <stdint.h>
 
 /*