Refactor Statistical Profiling Extensions implementation

Factor out SPE operations in a separate file.  Use the publish
subscribe framework to drain the SPE buffers before entering secure
world.  Additionally, enable SPE before entering normal world.

A side effect of this change is that the profiling buffers are now
only drained when a transition from normal world to secure world
happens.  Previously they were drained also on return from secure
world, which is unnecessary as SPE is not supported in S-EL1.

Change-Id: I17582c689b4b525770dbb6db098b3a0b5777b70a
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>
diff --git a/Makefile b/Makefile
index 9ab37ac..9894c5c 100644
--- a/Makefile
+++ b/Makefile
@@ -189,6 +189,7 @@
 				-Iinclude/lib/cpus/${ARCH}		\
 				-Iinclude/lib/el3_runtime		\
 				-Iinclude/lib/el3_runtime/${ARCH}	\
+				-Iinclude/lib/extensions		\
 				-Iinclude/lib/pmf			\
 				-Iinclude/lib/psci			\
 				-Iinclude/lib/xlat_tables		\