Separate out CASSERT macro into own header

Separate out the CASSERT macro out of bl_common.h into its own
header to allow more efficient header inclusion.

Change-Id: I291be0b6b8f9879645e839a8f0dd1ec9b3db9639
diff --git a/services/spd/tspd/tspd_private.h b/services/spd/tspd/tspd_private.h
index 69cf199..9eff9ec 100644
--- a/services/spd/tspd/tspd_private.h
+++ b/services/spd/tspd/tspd_private.h
@@ -35,6 +35,7 @@
 #include <arch.h>
 #include <psci.h>
 #include <tsp.h>
+#include <cassert.h>
 
 /*******************************************************************************
  * Secure Payload PM state information e.g. SP is suspended, uninitialised etc